A. Rationale

B. Rankings

C. Recommendations

1. Air

2. Water

3. Environmental Services

4. Environmental Sampling

5. Laundry and Bedding

6. Animals in Healthcare Facilities

7. Regulated Medical Waste

See PDF File

Appendix A - Glossary of Terms

Appendix B - Air (See other document)

Appendix C - Water

1. Biofilms

2. Water and Dialysate Sampling Strategies in Dialysis

3. Water Sampling Strategies and Culture Techniques for Detecting Legionellae

4. Procedure for Cleaning Cooling Towers and Related Equipment

5. Maintenance Procedures Used to Decrease Survival and Multiplication of Legionella spp. in Potable-Water Distribution Systems

Appendix D - Insects and Microorganisms

Appendix E - Evaluation Plan Elements

Appendix F - Information Resources

Appendix G - Areas of Future Research and Guideline Development

 

Part I, "Background Information: Environmental Infection Control in Healthcare Facilities," summarizes the major issues related to environmental infection control in healthcare facilities based on a comprehensive review of the scientific literature. Major attention is given to engineering and infection control concerns during construction, demolition, renovation, and repairs of healthcare facilities. Infection control measures used to recover from catastrophic events (e.g., flooding, sewage spills, loss of electricity and ventilation, disruption of the water supply) are reviewed. The limited impact of environmental surfaces, laundry, plants, animals, medical wastes, cloth furnishings, and carpeting on disease transmission in healthcare facilities is also explored.

Whenever possible, the recommendations in Part II are based on data from well-designed scientific studies. Some studies, however, have been conducted in narrowly-defined patient populations or for specific healthcare settings (e.g., hospitals versus long-term care facilities), making generalization of their findings to all situations potentially problematic.

Construction standards for hospitals or other healthcare facilities may not apply to residential home care units. Similarly, attempts to implement infection control measures indicated for immunosuppressed patient care are generally not necessary in those facilities where such patients are not present. Many of the recommendations are derived from empiric engineering concepts. Consequently, some of the recommendations may reflect an industry standard rather than an evidence-based conclusion. A few of the infection control measures proposed in this document cannot be rigorously evaluated for ethical or logistical reasons. Thus, some of the recommendations in Part II may be based on a strong theoretical rationale and suggestive evidence in the absence of confirmatory scientific evidence.

Finally, some of the recommendations are derived from existing federal regulations. The references and the appendices comprise Parts III and IV, respectively.

This guideline also identifies key process measurement elements to assist facilities in monitoring compliance with the evidence-based Category IA or IB recommendations provided in Part II. These include: 1) conducting risk assessment prior to construction, renovation, demolition, or major repair projects; 2) conducting ventilation assessments related to construction barrier installation; 3) establishing and maintaining appropriate pressure differentials for special care areas [e.g., operating rooms, airborne infection isolation, protective environments]; 4) evaluating non-tuberculous mycobacteria culture results for possible environmental sources; and 5) implementing infection control procedures to prevent environmental spread of antibiotic-resistant gram-positive cocci and assuring compliance with these procedures.

This document does not discuss: 1) industrial hygiene concerns of a non-infectious nature [e.g., "sick building syndrome" from chemicals and fumes, allergies]; 2) environmental issues in the home; 3) home health care; 4) bioterrorism; and 5) foodborne illness acquired in healthcare facilities. This document includes only limited discussion of: 1) handwashing/hand hygiene; 2) Standard Precautions; 3) infection control measures used to prevent instrument or equipment contamination during patient care [e.g., preventing waterborne contamination of nebulizers or ventilator humidifiers]; and 4) infection control measures used to prevent exposures of patients and staff to potentially infectious substances. These topics are mentioned only if they are important in minimizing the transfer of pathogens to and from persons or equipment and the environment. Although the document discusses principles of cleaning and disinfection as they are applied to maintenance of environmental surfaces, the full discussion of sterilization and disinfection of medical instruments and direct patient-care devices is deferred to a future guideline. Similarly, the full discussion of handwashing/hand hygiene, which was a major section in the Guideline for Handwashing and Hospital Environmental Control, is deferred to a future guideline devoted to this single topic.

This guideline was prepared by CDC staff members from the National Center for Infectious Diseases (NCID) and the National Center for Chronic Disease Prevention and Health Promotion (NCCDPHP) and the designated HICPAC sponsor. Contributors to this document reviewed mostly English-language manuscripts identified from reference searches using the National Library of Medicine’s MEDLINE, bibliographies of published articles, and infection control textbooks. Working drafts of the guideline were reviewed by CDC scientists, HICPAC committee members, and experts in infection control, engineering, internal medicine, infectious diseases, epidemiology, and microbiology. All the recommendations may not reflect the opinions of all reviewers.

Environmental disturbances associated with healthcare facility construction projects pose airborne and waterborne risks for the large number of patients who are at risk for healthcare-associated opportunistic infections. The increasing age of hospitals and healthcare facilities is also generating ongoing need for repair and remediation work (e.g., installing wiring for new information systems, removing old sinks, repairing elevator shafts) that can introduce or increase contamination of the air and water in patient-care environments. Aging equipment, deferred maintenance, and natural disasters provide additional mechanisms for the entry of environmental pathogens into high-risk patient-care areas.

Architects, engineers, construction contractors, environmental health scientists, and industrial hygienists have historically directed the design and function of hospitals’ physical plants. Increasingly, however, the growth in the number of susceptible patients and the increase in construction projects that can place these patients at risk for healthcare-associated infections call for the involvement of hospital epidemiologists and infection control professionals in plans for building, maintaining, and renovating healthcare facilities to minimize the adverse impact of the environment on the incidence of healthcare-associated infections.

Although Appendix A provides definitions for terms discussed in Part I, several terms which pertain to specific patient-care areas and patients who are at risk for healthcare-associated opportunistic infection are presented here. Specific engineering parameters for these care areas are discussed more fully in the text.

Airborne Infection Isolation (AII) refers to the isolation of patients infected with organisms that are spread via airborne droplet nuclei <5 µm in diameter. This isolation area is under negative pressure (i.e., externally exhausted), such that the direction of the air flow is from inside the room to the outdoors. The use of personal respiratory protection is also indicated for persons entering these rooms when occupied by a patient.

A Protective Environment (PE) is a specialized patient-care area, usually in a hospital, with a positive air flow relative to the corridor (i.e., air flows from the room to the outside adjacent space). The combination of high efficiency particulate air (HEPA) filtration, high numbers of air changes per hour (ACH), and minimal leakage of air into the room creates an environment which can safely accomodate patients who have undergone allogeneic hematopoietic stem cell transplant (HSCT) and other patients with severe and prolonged neutropenia.

Immunocompromised patients are those patients whose immune mechanisms are deficient because of immunologic disorders (e.g., human immunodeficiency virus [HIV] infection, congenital immune deficiency syndrome, chronic diseases [diabetes, cancer, emphysema, cardiac failure]) or immunosuppressive therapy (e.g., radiation, cytotoxic chemotherapy, anti-rejection medication, steroids). Immunocompromised patients who are identified as high-risk patients have the greatest risk of infection due to airborne or waterborne microorganisms. Patients in this subset include individuals who are severely neutropenic (i.e., <1,000 polymorphonuclear cells/µL for 2 weeks or <100 polymorphonuclear cells/mL for 1 week), allogeneic HSCT patients, and those who have received the most intensive chemotherapy (e.g., childhood amyeloid leukemia).

Moist environments and aqueous solutions in healthcare settings have the potential to serve as reservoirs for waterborne microorganisms. Under favorable environmental circumstances (e.g., temperature, source of nutrition), these microorganisms can proliferate to great numbers or may also remain for long periods in highly stable, environmentally-resistant yet infectious forms. Modes of transmission for waterborne infections include: 1) direct contact, such as during hydrotherapy; 2) ingestion of water, such as from consuming contaminated ice; 3) indirect-contact transmission, such as from an improperly reprocessed medical device;6 4) inhalation of aerosols dispersed from water sources;3 and 5) aspiration of contaminated water. The first three modes of transmission are commonly associated with infections due to gram-negative bacteria and non-tuberculous mycobacteria (NTM). Aerosols generated from water sources contaminated with Legionella spp. often serve as the vehicle for introducing these pathogens to the respiratory tract.376

Legionellosis is a collective term describing infection produced by Legionella spp., whereas Legionnaires’ disease is a multisystem illness with pneumonia.377 The clinical and epidemiologic aspects of these diseases, summarized in Table 16, are discussed extensively in another guideline.3 Although Legionnaires’ disease is a respiratory infection, infection control measures intended to prevent healthcare-associated cases center on water quality since the principal reservoir for Legionella spp. is water.

Legionella spp. are commonly found in various natural and manmade aquatic environments 378, 379 and can enter healthcare facility water systems in low or undetectable numbers.380, 381 Cooling towers, evaporative condensers, heated potable water distribution systems, and locally produced distilled water can provide environments for multiplication of legionellae.382 - 386 In several hospital outbreaks, patients were considered to be infected through exposure to contaminated aerosols generated by cooling towers, showers, faucets, respiratory therapy equipment, and room-air humidifiers.387 - 396 Factors that enhance colonization and amplification of legionellae in manmade water environments include: 1) temperatures of 25°- 42°C [77°F - 107.6°F];397 - 401 2) stagnation;402 3) scale and sediment;403 and 4) presence of certain free-living aquatic amoebae that can support intracellular growth of legionellae.403, 404 The bacteria multiply within single-cell protozoa in the environment and within alveolar macrophages in humans.

Other gram-negative bacteria present in finished or potable water can also cause healthcare-associated infections. Clinically important organisms in tap water include Pseudomonas aeruginosa, Pseudomonas spp., Burkholderia cepacia, Ralstonia pickettii, Stenotrophomonas maltophilia, and Sphingomonas spp. (Tables 17 and 18). These organisms are largely opportunistic; immunocompromised patients are at greatest risk of developing infection. Medical conditions associated with these bacterial agents range from colonization of the respiratory and urinary tracts to deep, disseminated infections that can result in pneumonia and bloodstream bacteremia. Colonization by any of these organisms often precedes the development of infection. The use of tap water in medical care (e.g., in direct patient care, as a diluent for solutions, as a water source for medical instruments and equipment, during the final stages of instrument disinfection), therefore presents a potential risk of exposure. Colonized patients can also serve as a source of contamination, particularly for moist environments of medical equipment (e.g., ventilators).

In addition to Legionella spp., Pseudomonas aeruginosa and Pseudomonas spp. are among the most important of the clinically-relevant, gram-negative, healthcare-associated pathogens identified from water. Pseudomonas spp., along with other gram-negative, non-fermentative bacteria, have minimal nutritional requirements (i.e., these organisms can grow in distilled water) and can tolerate a variety of physical conditions (e.g., temperature flucuations); these attributes are important for these organisms’ success as healthcare-associated pathogens and widespread distribution in moist environments. Measures to prevent the spread of these organisms and other waterborne gram-negative bacteria include handwashing, use of gloves and other barrier precautions; and eliminating potentially contaminated environmental reservoirs.444, 445.

Table 18. Other Gram-Negative Bacteria Associated with Water and Moist Environments

Two additional gram-negative bacterial pathogens which can proliferate in moist environments are Acinetobacter spp. and Enterobacter spp.549, 550 Members of both genera are responsible for healthcare-associated episodes of colonization, bloodstream infections, pneumonia, and urinary tract infections among medically-compromised patients, especially those in intensive care units and burn therapy units.544, 550 - 561 Infections due to Acinetobacter spp. represent a significant clinical problem. Average infection rates are higher during July - October compared to rates noted from November - June. 562 Mortality associated with Acinetobacter bacteremia ranges from 17% - 52%, and rates as high as 71% have been reported for pneumonia due to infection with either Acinetobacter spp. or Pseudomonas spp.552 - 554 Multi-drug resistance, especially concerning third generation cephalosporins for Enterobacter spp., contributes to increased morbidity and mortality.547, 550

Patients and healthcare workers represent important sources of either Acinetobacter spp. or Enterobacter spp., contributing to environmental contamination of surfaces and equipment, especially in intensive care areas because of the nature of the medical equipment (e.g., ventilators) and the moisture associated with this equipment.527, 549, 550, 563 Hand carriage and hand transfer are important factors for healthcare-associated transmission of these organisms, and for Serratia marcescens.564 Enterobacter spp. are primarily spread in this manner among patients by the hands of healthcare workers.545, 565 Acinetobacter spp. have been isolated from the hands of 4% to 33% of healthcare workers in some studies,563 - 568 and transfer of an epidemic strain of Acinetobacter from patients’ skin to healthcare workers’ hands has been demonstrated experimentally.569 Acinetobacter infections and outbreaks have been attributed to hand transfer of the organisms and to contaminated medical equipment and materials, especially devices that collect moisture (e.g., ventilators, cool mist humidifiers, vaporizers, mist tents) or have other contact with water of uncertain quality (e.g., rinsing a ventilator circuit in tap water).527 - 534 Strict adherence to hand hygiene or handwashing helps prevent the spread of both Acinetobacter spp. and Enterobacter spp.555, 570

Acinetobacter spp. have also been detected on a variety of dry environmental surfaces (e.g., bed rails, counters, sinks, bed cupboards, bedding, floors, telephones, medical charts) in the vicinity of colonized or infected patients.535 - 542 In two studies, the survival periods of A. baumannii and A. calcoaceticus on dry surfaces approximated that for Staphylococcus aureus (e.g., 26 - 27 days).571, 572 Because Acinetobacter spp. may come from numerous sources at any given time, laboratory investigation of healthcare-associated Acinetobacter infections may involve techniques to determine biotype, antibiotype, plasmid profile, and genomic fingerprinting (macrorestriction analysis) to accurately identify sources and modes of transmission of the organism(s).573

Non-tuberculous mycobacteria spp. (NTM) are acid-fast bacilli (AFB) commonly found in potable water. NTM include both saprophytic and opportunistic organisms. Many NTM are of low pathogenicity, and some measure of host impairment is necessary to enhance clinical disease.574 The four most common forms of human disease associated with NTM are: 1) pulmonary disease in adults; 2) cervical lymph node disease in children; 3) skin, soft tissue, and bone infections; and 4) disseminated disease in immunocompromised patients.574, 575 Person-to-person transmission of NTM infection does not appear to occur, and close contacts of patients are not readily infected, even though a patient may be shedding large numbers of organisms.574, 576 - 578 NTM are spread via all the modes of transmission associated with water. In addition to healthcare-associated outbreaks of clinical disease, NTM can colonize patients in healthcare facilities through consumption of contaminated water or ice, or inhalation of aerosols.579 - 583 Colonization following NTM exposure occurs when a patient’s local defense mechanisms are impaired; overt clinical disease is usually not described.584 Patients may have positive sputum cultures in the absence of clinical disease.

Using tap water during patient procedures, specimen collection and transport, or in the final steps of instrument reprocessing can result in pseudo-outbreaks of NTM contamination.598, 602, 603 NTM pseudo-outbreaks of M. chelonae, M. gordonae, and M. xenopi have been associated with both bronchoscopy and gastrointestinal endoscopy when tap water is used to provide irrigation to the site or to rinse off the viewing tip in situ, or if the instruments are inappropriately reprocessed with tap water in the final steps.597, 599, 604

NTM can be isolated from both natural and manmade environments. Numerous studies have identified various NTM in municipal water systems and in hospital water systems and storage tanks.587, 588, 596, 601, 605 - 609 Some NTM species (e.g., M. xenopi) can survive in water at 45°C (113°F), and can be isolated from hot water taps, which can pose a problem for hospitals that lower the temperature of their hot water systems.601 Other NTM (e.g., M. kansasii, M. gordonae, M. fortuitum, and M. chelonae) cannot tolerate high temperatures and are found associated more often with cold water lines and taps.606

NTM have a high degree of resistance to chlorine; they can tolerate free chlorine concentrations of 0.05 - 0.2 mg/L (0.05 -0.2 ppm) found at the tap.576, 610, 611 They are 20 - 100 times more resistant to chlorine compared to coliforms, and slow-growing strains of NTM appear to be more resistant to chorine inactivation compared to fast-growing NTM.612 Slow-growing NTM species (e.g., M. avium, M. kanasii) have also demonstrated some resistance to formaldehyde and glutaraldehyde, which has posed problems for reuse of hemodialyzers.31 The ability of NTM to form biofilms at fluid-surface interfaces (e.g., interior surfaces of water pipes) contributes to the organisms’ resistance to chemical inactivation and provides a microenvironment for growth and proliferation.613, 614

Cryptosporidium parvum is a protozoan parasite that causes self-limiting gastroenteritis in normal hosts but can cause severe, life-threatening disease in immunocompromised patients. First recognized as a human pathogen in 1976, C. parvum can be present in natural and finished waters after fecal contamination from either human or animal sources.615 –618

The health risks associated with drinking potable water contaminated with small numbers of C. parvum oocysts are unknown.619 It remains to be determined if immunosuppressed persons are more susceptible to lower doses of oocysts than are immunocompetent persons, or if strains of C. parvum vary in their infectious dose and their ability to cause disease. One study demonstrated that a median 50% infectious dose (ID50) of 132 oocysts was sufficient to cause infection among healthy volunteers.620 In a small study population of 17 healthy adults with pre-existing antibody to C. parvum, the ID50 was determined to be 1,880 oocysts, more than 20-fold higher than in seronegative persons.621 These data suggest that pre-existing immunity derived from previous exposures to Cryptosporidium offers some protection from infection and illness that ordinarily would result from exposure to low numbers of oocysts.621, 622

Oocysts, particularly those with thick walls, are environmentally resistant, but their survival in water is poorly understood.618 The prevalence of Cryptosporidium in the United States drinking water supply is, however, notable. Two surveys of approximately 300 surface water supplies revealed that 55% - 77% of the water samples contained Cryptosporidium oocysts.623, 624 Because the oocysts are highly resistant to common disinfectants (e.g., chlorine) used to treat drinking water, filtration of the water is important in reducing the risk of waterborne transmission. Coagulation-floculation and sedimentation, when used with filtration, can collectively achieve approximately a 2.5 log10 reduction in the number of oocysts.625 However, outbreaks have been associated with both filtered and unfiltered drinking water systems (e.g., the 1993 outbreak in Milwaukee, Wisconsin, that affected 400,000 people).618, 626 - 628

The presence of oocysts in the water is not an absolute indicator that infection will occur when the water is consumed, nor does the absence of detectable oocysts guarantee that infection will not happen. Healthcare-associated outbreaks of cryptosporidiosis have been described primarily among groups of elderly patients and immunocompromised persons.629

Treated municipal water comes into a healthcare facility via the water mains and is distributed throughout the building(s) by a network of pipes constructed of galvanized iron, copper, and polyvinylchloride (PVC). The pipe runs should be as short as practical. Where recirculation is employed, the pipe runs should be insulated and long, dead legs avoided in efforts to minimize the potential for water stagnation to occur which favors the proliferation of Legionella and NTM in the system. In high-risk applications insulated recirculation loops should be incorporated as a design feature.

Each water service main, branch main, riser, and branch (to a group of fixtures) has a valve and a means to reach the valves via an access panel.120 Each fixture has a stop valve. Valves permit the isolation of a portion of the water system within a facility during repairs or maintenance. Vacuum breakers in the lines prevent water from back-flowing into the system.

Healthcare facilities generate hot water from mains water using a boiler system. Hot water heaters and storage vessels for such systems should have a drainage facility at the lowest point and the heating element should be located as close as possible to the bottom of the vessel to facilitate mixing and prevent water temperature stratification. Those hot or cold water systems which incorporate an elevated holding tank should be inspected and cleaned annually. Lids should fit closely to exclude foreign materials.

The most common point-of-use fixtures for water in patient-care areas are sinks, faucets, aerators, showers, and toilets; eye-wash stations are found primarily in laboratories. The potential for these fixtures to serve as a reservoir for pathogenic microorganisms has long been recognized (Table 20).489, 630 - 632 Wet surfaces and the production of aerosols facilitate the multiplication of and dispersion of microbes. The level of risk associated with aerosol production from point-of-use fixtures varies. Aerosols from shower heads and aerators have been linked to a limited number of clusters of gram-negative bacterial colonizations and infections, including Legionnaires’ disease, especially in areas where immunocompromised patients are present (e.g., surgical intensive care units, transplant units, and oncology units).393, 396, 632 - 635

In one report, clinical infection was not evident among immunocompetent persons (e.g., hospital staff) who used hospital showers when L. pneumophila was present in the water system.636 Given the infrequency of reported outbreaks associated with faucet aerators, expert opinion on the removal of these devices from general use is mixed. If additional clusters of infections or colonizations occur in high-risk patient-care areas, then it may be prudent to clean and decontaminate the aerators or remove them.634, 635

ASHRAE recommends cleaning and monthly disinfection of aerators in high-risk patient-care areas as part of Legionella control measures.637 Although aerosols are produced with toilet flushing,638, 639 there is no epidemiologic evidence to suggest that these aerosols pose a direct infection hazard. Although not considered a standard point-of-use fixture, decorative fountains are increasingly being installed in

healthcare facilities and other public buildings. Aerosols from a decorative fountain in a hotel lobby transmitted L. pneumophila serogroup 1 infection to a small cluster of older adults.640 The fountain had been irregularly maintained, and water in the fountain may have been heated by submersed lighting, all of which favored the proliferation of Legionella in the system.640 Because of the potential for generations of infectious aerosols, a prudent prevention measure is to avoid locating these fixtures in or near high-risk patient-care areas and to adhere to written policies for routine maintenance of fountains that are installed.

Hot water temperature is usually measured at the point of use or at the point at which the water line enters equipment requiring hot water for proper operation.120 Generally the hot water temperature in patient-care areas is no greater than 43°C (110°F),120 and many states have adopted this temperature setting into their healthcare regulations and building codes. ASHRAE, however, has recommended higher settings.637 Steam jets or booster heaters are usually needed to meet the hot water temperature requirements in service areas of the hospital such as the kitchen (49°C [120°F]) or the laundry (71°C [160°F]).120 Additionally, there may be other needs for water lines running a particular temperature specified by manufacturers of specific hospital equipment. Hot-water distribution systems serving patient-care areas are generally operated under constant recirculation to provide continuous hot water at each hot water outlet.120 If a facility is or has a hemodialysis unit, then continuously circulated, cold treated water is provided to that unit.120

To minimize the growth and persistence of gram-negative waterborne bacteria (e.g., thermophilic NTM, Legionella spp.),601, 671 - 677 cold water in healthcare facilities should be stored and distributed at temperatures below 20°C (68°F); hot water should be stored above 60°C (140°F) and circulated with a minimum return temperature of 51°C (124°F),637 or the highest temperature specified in state regulations and building codes. If the temperature setting of 51°C (124°F) is permitted, then installation of preset thermostatic mixing valves can help to prevent scalding. New shower systems in large buildings, hospitals, and nursing homes should be designed to permit mixing of hot and cold water near the shower head. The warm water section of pipe between the control valve and shower head should be self-draining. Where buildings cannot be retrofitted, other approaches to minimize the growth of Legionella spp. include periodically increasing the temperature to at least 66°C (150°F) at the point of use (i.e., faucets) or chlorinating followed by flushing the water.637, 678, 679 Systems should be inspected annually to ensure that thermostats are functioning properly.

Adequate water pressure ensures sufficient water supplies for: 1) direct patient care; 2) operation of water-cooled instruments and equipment [e.g., lasers, computer systems, telecommunications systems, automated endoscope reprocessors 680 ]; 3) proper function of vacuum suctioning systems; 4) indoor climate control; and 5) fire protection systems. Maintaining adequate pressure also helps to insure the integrity of the piping system.

Corrective measures for water system failures have not been studied in well-designed experiments, but rather are based on empiric engineering and infection control principles. Healthcare facilities can occasionally sustain intentional cut-offs by the municipal water authority to permit new construction project tie-ins and unintentional breaks in service when a water main breaks due to aging infrastructure or a construction accident. Vacuum breakers or other similar devices can prevent backflow of water in the facility’s distribution system during water-disruption emergencies.11 To be prepared for such an emergency, all healthcare facilities need contingency plans that identify: 1) the total demand for potable water; 2) the quantity of replacement water (e.g., bottled water) required for a minimum of 24 hours when the water system is down; 3) mechanisms for emergency water distribution; and 4) procedures for correcting drops in water pressure that affect operation of essential devices and equipment that are driven or cooled by a water system.

Detailed current plans for hot and cold water piping systems should be readily available for maintenance and repair purposes in case of system problems. Opening potable water systems for repair or construction and subjecting systems to water-pressure changes can result in water discoloration and dramatic increases in the concentrations of Legionella spp. and other gram-negative bacteria. The maintenance of a chlorine residual at all points within the piping system also offers some protection from entry of contamination to the pipes in the event of an inadvertent cross- connection between potable and non-potable water lines. As a minimum preventive measure, ASHRAE recommends a thorough flushing of the system.637 High-temperature flushing or chlorination may also be appropriate strategies to decrease potentially high concentrations of waterborne organisms. The decision to pursue either of these remediation strategies, however, should be made on a case-by-case basis. If only a portion of the system is involved, high temperature flushing or chlorination may be used on only that portion of the system.637

When shock decontamination of hot water systems is necessary (e.g., after disruption due to construction, cross-connections), the hot water temperature should be raised to 71°C - 77°C (160°F - 170°F) and maintained at that level while progressively flushing each outlet around the system. A minimum flush time of 5 minutes has been recommended;3 the optimal flush time is not known, however, and longer flush times may be necessary.681 The number of outlets that can be flushed simultaneously depends on the capacity of the water heater and the flow capability of the system. Appropriate safety procedures to prevent scalding are essential. When possible, flushing should be performed when the fewest building occupants are present (e.g., nights and weekends).

When thermal shock treatment is not possible, shock chlorination may provide an alternative.637 Experience with this method of decontamination is limited, however, and high levels of free chlorine can corrode metals. Chlorine should be added, preferably overnight, to achieve a free chlorine residual of at least 2 mg/L (2 ppm) throughout the system.637

This may require chlorination of the water heater or tank to levels of 20 - 50 mg/L (20 - 50 ppm). The pH of the water should be maintained between 7.0 and 8.0. 637 After completion of the decontamination, recolonization of the hot water system is likely to occur unless proper temperatures are maintained or a procedure such as continuous supplemental chlorination is continued.

Interruptions of the water supply and sewage spills are situations which require immediate recovery and remediation measures to assure the health and safety of patients and staff.682 When delivery of potable water through the municipal distribution system has been disrupted, the public water supplier must issue a "boil water" advisory if microbial contamination presents an immediate public health risk to customers. The hospital engineer should oversee the restoration of the water system in the facility and clear it for use when appropriate to do so. Hospitals must maintain a high level of surveillance for waterborne disease among patients and staff after the advisory is lifted.619

Flooding from either external (e.g., from a hurricane) or internal sources (e.g., a water system break) usually results in property damage and a temporary loss of water and sanitation.683 – 685

The JCAHO requires all hospitals have plans which address facility response for recovery from both internal and external disasters.686 The plans are required to address: 1) general emergency preparedness; 2) staffing; 3) regional planning among area hospitals; 4) emergency supply of potable water; 5) infection control and medical services needs; 6) climate control; and 7) remediation. The basic principles of structural recovery from flooding are similar to those for recovery from sewage contamination. Tables 21 - 23 summarize actions that will help to restore facility function and operations after water disruptions, sewage spills, and flooding. Medical records should be allowed to dry, and either photocopied or placed in plastic covers before returning them to the record. Moisture meters can be used to assess water-damaged structural materials.

An exception to these recommendations is made for hemodialysis units where water is further treated either by portable water treatment or large-scale water treatment systems usually involving reverse osmosis (RO).

In the United States, greater than 98% of dialysis facilities use RO treatment for their water.687 It may be prudent, however, to change out pre-treatment filters and disinfect the system to prevent colonization of the RO membrane and microbial contamination down-stream of the pre-treatment filter.

a. Some cooling towers may use a potable water source, but most units use non-potable water.

In addition to using supplemental treatment methods as remediation measures after inadvertent contamination of water systems, healthcare facilities sometimes use special measures to control waterborne microorganisms on a sustained basis.

This decision is most often associated with outbreaks of legionellosis and subsequent efforts to control legionellae,688 although some facilities have tried supplemental measures to better control thermophilic NTM.601

The primary disinfectant for both cold and hot water systems is chlorine. However, chlorine residuals are expected to be low, and possibly nonexistent, in hot water tanks due to extended retention time in the tank and elevated water temperature. Flushing, especially that which removes sludge from the bottom of the tank, probably provides the most effective treatment of water systems. Unlike the situation for disinfecting cooling towers, there are no equivalent recommendations for potable water systems, although specific intervention strategies have been published.389, 689 The principal approaches to disinfection of potable systems are heat flushing using temperatures 71°C - 77°C (160°F -170° F), hyperchlorination, and physical cleaning of hot water tanks.3, 389, 637 Potable systems are easily recolonized and may require continuous intervention such as raising of hot water temperatures or continuous chlorination.389, 679

Some hospitals with hot water systems identified as the source of Legionella spp. have decontaminated their systems by pulse (one-time) thermal disinfection/superheating and hyperchlorination.679, 681, 690, 691 After either of these procedures, hospitals either maintain their hot water at >51°C (>124°F) or <20°C (<68°F) at the tap or chlorinate their hot water to achieve 1-2 mg/L (1-2 ppm) of free residual chlorine at the tap.26, 436, 677 - 679, 692, 693 Additional measures (e.g., physical cleaning or replacement of hot-water storage tanks, water heaters, faucets, and showerheads) may be required to help eliminate accumulations of scale and sediment that protect organisms from the biocidal effects of heat and chlorine.398,

679 Alternative methods for controlling and eradicating legionellae in water systems (e.g., treating water with ozone, UV light, heavy metal ions [i.e., copper/silver ions]) have limited the growth of legionellae under laboratory and/or operating conditions.694 - 705 However, results from a recent study suggest that legionellae develop tolerance to copper/silver ion treatment during extended application (>4 years);706 further studies on the long-term efficacy of these treatments are needed, however, before they can be considered standard precautions.

Renewed interest in the use of chloramines stems from concerns about adverse health effects associated with disinfectants and disinfection by-products.707 Monochloramine usage minimizes the formation of disinfection by-products, including trihalomethanes and haloacetic acids. Monochloramines can also reach distal points in a water system and can penetrate into bacterial biofilms more effectively than free chlorine.708 It should be noted that monochloramine use is limited to municipal water treatment plants and is currently not available to healthcare facilities as a supplemental water treatment approach. A recent study indicated that 90% of Legionnaires’ disease outbreaks associated with drinking water could have been prevented if monochloramine rather than free chlorine was used for residual disinfection.709 In a retrospective comparison of healthcare-associated Legionnaires’ disease incidence in Central Texas hospitals, the same research group documented an absence of cases in facilities located in communities with monochloramine-treated municipal water.710

Additional filtration of potable water systems is not routinely necessary. Filters are used in water lines in dialysis units, however, and may be inserted into the lines for specific equipment (e.g., endoscope washer/disinfectors) for the purpose of providing bacteria-free water for instrument reprocessing. Additionally, a reverse osmosis (RO) unit is usually added to the distribution system leading to PE areas.

The primary and secondary environmental infection control strategies described below pertain to healthcare facilities without transplant. Infection control measures specific to PE or transplant units (patient-care areas housing patients at the highest risk for morbidity and mortality due to Legionella spp. infection) are described in the subsection entitled "Preventing Legionnaires’ Disease in Protective Environments."

Healthcare facilities use at least two general strategies to prevent healthcare-associated legionellosis when no cases or only sporadic cases have been detected. The first is an environmental surveillance approach, with periodic culturing of water samples from the hospital’s potable water system to monitor for Legionella spp.711 - 714 If any sample is culture-positive, diagnostic testing is recommended for all patients with healthcare-associated pneumonia.712, 713 In-house testing is recommended for facilities with transplant programs. If >30% of the samples are culture-positive for Legionella spp., decontamination of the facility’s potable water system is recommended.712 The premise for this approach is that no cases of healthcare-associated legionellosis can occur if Legionella spp. are not present in the potable water system, and, conversely, cases of healthcare-associated legionellosis could potentially occur if Legionella spp. are cultured from the water.26, 715 Physicians informed that the hospital’s potable water system is culture-positive for Legionella spp. are more likely to order diagnostic tests for legionellosis.

A potential advantage of the environmental surveillance approach is that periodic culturing of water is less costly than routine laboratory diagnostic testing for all patients who have healthcare-associated pneumonia. The main argument against this approach is that, in the absence of cases, the relationship between water culture results and legionellosis risk remains undefined.3 Legionnella spp. can be present in the water systems of buildings,716 often without being associated with known cases of disease.436, 675, 717 In a study of 84 hospitals in Québec, 68% of the water systems were found to be colonized with Legionella spp., and 26% were colonized at greater than 30% of sites sampled; cases of Legionnaires’ disease, however, were infrequently reported from these hospitals.675

Other factors also argue against environmental surveillance. Interpretation of results from periodic water culturing might be confounded by differing results among the sites sampled in a single water system and by fluctuations in the concentration of Legionella spp. at the same site.677, 718 In addition, the risk for illness after exposure to a given source might be influenced by a number of factors other than the presence or concentration of organisms; these factors include: 1) the degree to which contaminated water is aerosolized into respirable droplets; 2) the proximity of the infectious aerosol to the potential host; 3) the susceptibility of the host; and 4) the virulence properties of the contaminating strain.719 - 721 Thus, data are insufficient to assign a level of disease risk even on the basis of the number of colony-forming units detected in samples from areas for immunocompetent patients.

Conducting environmental surveillance would obligate hospital administrators to initiate water-decontamination programs if Legionella spp. Are identified. Because of these problems, periodic monitoring of water from the hospital's potable water system and from aerosol-producing devices is not widely recommended in facilities that have not experienced cases of healthcare-associated legionellosis.637, 722

The second strategy to prevent and control healthcare-associated legionellosis is a clinical approach in which providers maintain a high index of suspicion for legionellosis and order appropriate diagnostic tests (i.e., culture, urine antigen, direct fluorescent antibody [DFA] serology) for patients with healthcare-associated pneumonia who are at high risk for legionellosis and its complications.436, 723, 724 Testing autopsy specimens can be included in this strategy should a death due to healthcare-associated pneumonia occur. Identification of one case of definite or two cases of possible healthcare-associated Legionnaires’ disease prompts an epidemiologic investigation for a hospital source of Legionella spp. This may involve culturing the facility’s water for Legionella spp. Routine maintenance of cooling towers and using only sterile water for the filling and terminal rinsing of nebulization devices and ventilation equipment help to minimize potential sources of contamination.

The indications for a full-scale environmental investigation to search for and subsequently decontaminate identified sources of Legionella spp. in healthcare facilities without transplant units have not been clarified, and these indications probably differ depending on the facility. Case categories for healthcare-associated Legionnaires’ disease in facilities without transplant units include definite cases (i.e., laboratory-confirmed cases of legionellosis that occur in patients who have been hospitalized continuously for >10 days before the onset of illness) and possible cases (i.e., laboratory- confirmed infections that occur 2 - 9 days after hospital admission).3 In settings in which as few as 1 - 3 healthcare-associated cases are recognized over several months, intensified surveillance for Legionnaires’ disease has frequently identified numerous additional cases.385, 391, 394, 430, 705, 723 This finding suggests the need for a low threshold for initiating an investigation after laboratory confirmation of cases of healthcare-associated legionellosis. When developing a strategy for responding to such an identification, however, infection control personnel should consider the level of risk for healthcare-associated acquisition of, and mortality from, Legionella spp. infection at their particular facility.

An epidemiologic investigation conducted to determine the source of Legionella spp. involves several important steps. (Table 24). Laboratory assistance is important in supporting epidemiologic evidence of a link between human illness and a specific environmental source.725 Strain determination from subtype analysis is most frequently used in these investigations.396, 726- 728 Once the environmental source is established and confirmed with laboratory support, supplemental water treatment strategies can be initiated as appropriate.

The decision to search for hospital environmental sources of Legionella spp. and the choice of procedures to eradicate such contamination are based on several considerations: 1) the hospital’s patient population; 2) the cost of an environmental investigation and institution of control measures to eradicate Legionella spp. from the water supply;729, 730 and 3) the differential risk, based on host factors, for acquiring healthcare-associated legionellosis and developing severe and fatal infection.

This subsection outlines infection control measures applicable to those healthcare facilities providing care to severely neutropenic patients, as indigenous microorganisms in the tap water of these facilities may pose problems for such patients. These measures, summarized in Table 25, are designed to prevent the generation of potentially infectious aerosols from water and the subsequent exposure of PE patients or other immunocompromised patients (e.g., transplant patients). Infection control measures that address the use of water with medical equipment such as ventilators, nebulizers, and equipment humidifiers are described in other guidelines.3

When one case of laboratory-confirmed, healthcare-associated Legionnaires’ disease is identified in a patient in PE (i.e., an inpatient in PE for all or part of the 2 - 10 days prior to onset of illness), or if two or more cases of laboratory-confirmed cases occur among patients who had visited an outpatient PE setting, the hospital should report the cases to the local and state health departments and initiate a thorough epidemiologic and environmental investigation to determine the likely environmental sources of Legionella spp.9 The source of Legionella should be decontaminated or removed.

Isolated cases may be difficult to investigate. Because transplant recipients are at much higher risk for disease and death from legionellosis compared to most other hospitalized patients, periodic culturing for Legionella spp. in water samples from the PE unit’s potable water supply may be considered as part of an overall strategy to prevent Legionnaires’ disease in PE units.9, 430 The optimal methodology (i.e., frequency, number of sites) for environmental surveillance cultures in PE units has not been determined, and the cost-effectiveness of this strategy has not been evaluated. Because transplant recipients are at high risk of Legionnaires’ disease and there are no data to determine a safe concentration of legionellae organisms in potable water, the goal, if environmental surveillance for Legionella spp. is undertaken, should be to maintain water systems with no detectable organisms.9, 430 Culturing for legionellae may be used to assess the effectiveness of water treatment or decontamination methods, which provides a benefit to both patients and healthcare workers.731

Protecting patient-care devices and instruments from inadvertent tap water contamination during room cleaning procedures is also important in any immunocompromised patient care area. In a recent outbreak of gram-negative bacteremias among open-heart-surgery patients, pressure-monitoring equipment which was assembled and left uncovered overnight prior to the next day’s surgeries was inadvertently contaminated with mists and splashing water from a hose-disinfectant system used for cleaning.732

Modern healthcare facilities maintain indoor climate control during the summer by use of cooling towers for large facilities or evaporative condensers for smaller buildings. A cooling tower is a wet-type, evaporative heat transfer device used to discharge to the atmosphere waste heat from a building’s air conditioning condensers (Figure 5).733, 734 Warm water from air-conditioning condensers is piped to the cooling tower where it is sprayed downward into a counter- or cross-current air flow. To accelerate heat transfer to the air, the water passes over the fill, which either breaks water into droplets or causes it to spread into a thin film.733, 734 Most systems use fans to move air through the tower, although some large industrial cooling towers rely on natural draft circulation of air. The cooled water from the tower is piped back to the condenser where it again picks up heat generated during the process of chilling the system’s refrigerant. The water is cycled back to the cooling tower to be cooled. Closed-circuit cooling towers and evaporative condensers are also evaporative heat transfer devices. In these systems, the process fluid (i.e., a liquid such as water, ethylene glycol/water mixture, oil, etc. or a condensing refrigerant) does not directly contact the cooling air, but is contained inside a coil assembly.637

Figure 5. Diagram of a Typical Air Conditioning (Induced Draft) Cooling Tower. a

Cooling towers and evaporative condensers incorporate inertial stripping devices called drift eliminators to remove water droplets generated within the unit. While the effectiveness of these eliminators varies significantly based on their design and condition, some water droplets in the size range of <5 µm will likely leave the unit, and some larger droplets leaving the unit may be reduced to <5 µm by evaporation. Thus, even with proper operation, a cooling tower or evaporative condenser can generate and expel respirable water aerosols. If either the water in the unit’s basin or the make-up water (added to replace water lost to evaporation) contains Legionella spp. or other waterborne microorganisms, these organisms can be aerosolized and dispersed from the unit.735 Clusters of both Legionnaires’ disease and Pontiac fever have been traced to exposure to infectious water aerosols originating from cooling towers and evaporative condensers contaminated with Legionella spp. Although the majority of these outbreaks have been community-acquired episodes of pneumonia,736 - 743 there have been instances of healthcare-associated Legionnaires’ disease linked to cooling tower aerosol exposure.390, 391 Contaminated aerosols from cooling towers on hospital premises gained entry to the buildings either through open windows or via air handling system intakes located near the tower equipment. Cooling towers and evaporative condensers provide ideal ecological niches for Legionella spp. The typical temperature of the water in cooling towers ranges from 29°C - 35°C (85°F - 95°F), although temperatures can be above 49°C (120°F) and below 21°C (70°F) depending on system heat load, ambient temperature and operating strategy.637

An Australian study of cooling towers found that legionellae colonized or multiplied in towers with basin temperatures above 16°C (60.8°F), and multiplication became explosive at temperatures above 23°C (73.4°F).744 Water temperature in closed circuit cooling towers and evaporative condensers is similar to that in cooling towers. Considerable variation in the piping arrangement occurs. Stagnant areas or dead legs may be difficult to clean or penetrate with biocides.

Several documents address the routine maintenance of cooling towers, evaporative condensers, and whirlpool spas.637, 745 - 748 They suggest following manufacturer's recommendations for cleaning and biocide treatment of these devices; all healthcare facilities should provide proper maintenance for their cooling towers and evaporative condensers, even in the absence of Legionella spp. A general protocol for cleaning cooling towers is given in Appendix C. Since cooling towers and evaporative condensers may be shut down during periods when air conditioning is not needed, it is important to perform this maintenance cleaning and treatment before starting up the system for the first time in the season.743

Emergency decontamination protocols describing cleaning procedures and hyperchlorination for cooling towers have been developed for towers implicated in the transmission of legionellosis.747, 748

Hemodialysis, hemofiltration, and hemodiafiltration require special water treatment processes to prevent adverse patient outcomes of dialysis therapy due to improper formulation of dialysate with water containing high levels of certain chemical or biological contaminants. The Association for the Advancement of Medical Instrumentation (AAMI) has established chemical and microbiologic standards for the water used to prepare dialysate, substitution fluid, or to reprocess hemodialyzers for renal replacement therapy.749 - 752 The AAMI standards address: 1) equipment and processes used to purify water for the preparation of concentrates and dialysate, and the reprocessing of dialyzers for multiple use; and 2) the devices used to store and distribute this water. Future revisions to these standards may include hemofiltration and hemodiafiltration.

Water treatment systems used in hemodialysis use several physical and/or chemical processes either singly or in combination. A schematic diagram of basic water treatment components in dialysis is given in Figure 6. These systems may be portable units or large systems which feed several rooms. In the United States, more than 97% of maintenance hemodialysis facilities use reverse osmosis (RO) alone or in combination with deionization.753 Many acute-care facilities use portable hemodialysis machines with attached portable water treatment systems that use either deionization or RO.

These machines were exempted from earlier versions of AAMI recommendations, but given current knowledge about toxic exposures to and inflammatory processes in patients new to dialysis, these should now come into compliance with current AAMI recommendations for hemodialysis water and dialysate quality.749, 750 Previous recommendations had been based on the assumption that acute-care patients did not experience the same degree of adverse effects from short-term, cumulative exposures to either chemicals or microbiologic agents present in hemodialysis fluids, compared to the risks encountered by patients during chronic, maintenance dialysis.749, 750 Additionally, the JCAHO is now reviewing inpatient dialysis (acute and maintenance) for compliance with the AAMI standards and recommended practices.

Neither the water used to prepare dialysate nor the dialysate itself needs to be sterile, but tap water cannot be used without additional treatment. Infections due to rapid-growing NTM (e.g., Mycobacterium chelonae, M. abscessus) present a potential risk to hemodialysis patients, especially those in hemodialyzer reuse programs, if disinfection procedures to inactivate mycobacteria in the water (low-level disinfection) and the hemodialyzers (high-level disinfection) are inadequate.31, 32, 610 Other factors relating to microbial contamination in dialysis systems could involve the water treatment system, the water and dialysate distribution systems, and in some cases, the type of hemodialyzer.642, 643, 754 - 759

Understanding the various factors and their influence on contamination levels is the key to preventing high levels of microbial contamination in dialysis therapy. In several studies, pyrogenic reactions were shown to be caused by lipopolysaccharide or endotoxin associated with gram-negative bacteria.754, 760 - 763

Early studies demonstrated that parenteral exposure to endotoxin at a concentration of 1 ng/kg body weight/hour was the threshold dose for producing pyrogenic reactions in humans, and that the relative potencies of endotoxin differ by bacterial species.764, 765 Gram-negative water bacteria (e.g., Pseudomonas spp.) have been shown to multiply rapidly in a variety of hospital-associated fluids that can be used as supply water for hemodialysis (e.g., distilled water, deionized water, RO water, softened water) and in dialysate (a balanced salt solution made with this water).766 Several studies have demonstrated that the attack rates of pyrogenic reactions are related directly to the number of bacteria in dialysate.642, 643, 767 These studies provided the rationale for setting the heterotrophic bacteria standards in the first AAMI hemodialysis guideline at #2,000 colony forming units per milliliter (CFU/mL) in dialysate and one log lower (#200 CFU/mL) for the water used to prepare dialysate.644, 749 If the level of bacterial contamination exceeded 200 CFU/mL in water, this level could be amplified in the system and effectively constitute a high inoculum for dialysate at the start of a dialysis treatment.767, 768 Pyrogenic reactions did not appear to occur when the level of contamination was below 2,000 CFU/mL in dialysate unless the source of the endotoxin was exogenous to the dialysis system (i.e., present in the community water supply). Endotoxins in a community water supply have been linked to the development of pyrogenic reactions among dialysis patients.754

The issue as to whether endotoxin actually crosses the dialyzer membrane is controversial. Several investigators have shown that bacteria, growing in dialysate, generated products that could cross the dialysis membrane.769, 770 Gram-negative bacteria growing in dialysate have been shown to produce endotoxins that in turn stimulated the production of anti-endotoxin antibodies in hemodialysis patients.761, 771 These data suggest that bacterial endotoxins, although relatively large molecules, do indeed cross dialysis membranes, either intact or as fragments. The use of the very permeable membranes known as high-flux membranes (which allow large molecules [e.g., $2 microglobulin] to traverse the membrane) increases the potential for passage of endotoxins into the blood path. Several studies support this contention. In one such study, an increase in plasma endotoxin concentrations during dialysis was observed when patients were dialyzed against dialysate containing 10 3 - 10 4 CFU/mL Pseudomonas spp.772 In vitro studies using both radiolabeled lipopolysaccharide and biological assays have demonstrated that biologically active substances derived from bacteria found in dialysate can cross a variety of dialysis membranes.762, 773 - 776

Patients treated with high-flux membranes are reported to have higher levels of anti-endotoxin antibodies than normal subjects or patients treated with conventional membranes.777 Finally, since 1989, 19% - 22% of dialysis centers have reported pyrogenic reactions in the absence of septicemia.778, 779

Investigations of adverse outcomes among patients using reprocessed dialyzers demonstrated a greater risk of developing pyrogenic reactions when the water used to reprocess these devices contained > 6 ng/mL endotoxin and > 10 4 CFU/mL bacteria.780 In addition to the variability in endotoxin assays, there are also host factors involved in determining whether a patient will mount a response to endotoxin.763 Outbreak investigations of pyrogenic reactions and bacteremias associated with hemodialyzer reuse have demonstrated that pyrogenic reactions are prevented once the endotoxin level in the water used to reprocess the dialyzers is returned to below the AAMI standard level.781

Reuse of dialyzers, use of bicarbonate dialysate, high-flux dialyzer membranes, or high-flux dialysis may increase the potential for pyrogenic reactions if the water in the dialysis setting does not meet standards.756 - 758

Although investigators have not been able to demonstrate endotoxin transfer across dialysis membranes,763, 782, 783 the preponderance of reports now supports the ability of endotoxin to transfer across at least some high-flux membranes under some operating conditions. In addition to the acute risk of pyrogenic reactions, there is increasing indirect evidence that chronic exposure to low amounts of endotoxin may play a role in some of the long-term complications of hemodialysis therapy. Patients treated with ultrafiltered dialysate for 5-6 months have demonstrated a decrease in serum $2- microglobulin concentrations and a decrease in markers of an inflammatory response.784 - 786 In studies of longer duration, use of microbiologically ultrapure dialysate has been associated with a decreased incidence of $2- microglobulin-associated amyloidosis.787, 788

The current AAMI standard does not provide for endotoxin testing of all dialysis fluids. Only water that is used for the reprocessing of hemodialyzers has an endotoxin limit of 5 endotoxin units per milliliter (EU/mL [Table 26]), and the current standard recommends this as a choice. CDC has advocated monthly endotoxin testing along with microbiological assays of water since endotoxin activity may not correspond to the total heterotrophic plate counts.789

Consequently, the proposed revision to the AAMI standard may impose an upper limit on the endotoxin content of all water for hemodialysis applications. A level of 2 EU/mL was chosen as the upper limit for endotoxin because this level is easily achieved with contemporary water treatment systems using RO and/or ultrafiltration. Because 48 hours can elapse between the time of sampling water for the determination of microbial contamination and the time when results are received, and because bacterial proliferation can be rapid, action levels for microbial counts and endotoxin concentrations are also being considered in this revision of the standard. These will allow users to initiate corrective action before levels exceed the maximum levels established by the standard.

In hemodialysis, the net movement of water is from the blood to the dialysate, although within the dialyzer there may be local movement of water from the dialysate to the blood through the phenomenon of back-filtration, particularly in dialyzers with highly permeable membranes.790 In contrast, hemofiltration and hemodiaflltration feature infusion of large volumes of electrolyte solution (20 - 70 L) into the blood. Increasingly, this electrolyte solution is being prepared on-line from water and concentrate. Because of the large volumes of fluid infused, AAMI considered the necessity of setting more stringent requirements for water to be used in this application, but has not yet established these due to lack of expert consensus. On-line hemofiltration and hemodiafiltration systems use sequential ultrafiltration as the final step in the preparation of infusion fluid. Several experts from AAMI felt that these point-of-use ultrafiltration systems should be capable of further reducing the bacteria and endotoxin burden of solutions prepared from water meeting the requirements of the AAMI standard to a safe level for infusion.

The strategy for controlling massive accumulations of gram-negative water bacteria and NTM in dialysis systems primarily involves preventing their growth through proper disinfection of water treatment system and hemodialysis machines. Gram-negative water bacteria, their associated lipopolysaccharides (bacterial endotoxins), and NTM ultimately come from the community water supply, and levels of these bacteria can be amplified depending on the water treatment system, dialysate distribution system, type of dialysis machine, and method of disinfection (Table 27).610, 754, 791

Control strategies are designed to reduce levels of microbial contamination in water and dialysis fluid to relatively low levels but not to completely eradicate it. Two components of hemodialysis water distribution systems – pipes and storage tanks – can serve as reservoirs of microbial contamination. Hemodialysis systems frequently use pipes that are wider and longer than are needed to handle the required flow. This slows the fluid velocity and increases both the total fluid volume and the wetted surface area of the system. Gram-negative bacteria in fluids remaining in pipes overnight multiply rapidly and colonize the wet surfaces, producing bacterial populations and endotoxin quantities in proportion to the volume and surface area. Such colonization results in formation of protective biofilm that is difficult to remove and protects the bacteria from disinfection.792

Routine low-level disinfection of the pipes on a weekly basis can help to control bacterial contamination of the distribution system. Additional measures to protect pipes from contaminations include: 1) situating all outlet taps at equal elevation and at the highest point of the system so that the disinfectant cannot drain from pipes by gravity before adequate contact time has elapsed; and 2) eliminating rough joints, dead-end pipes, and unused branches and taps that can trap fluid and serve as reservoirs of bacteria capable of continuously inoculating the entire volume of the system.760

A storage tank in the distribution system greatly increases the volume of fluid and surface area available and can serve as a niche for water bacteria. Storage tanks are therefore not recommended for use in dialysis systems unless they are frequently drained and adequately disinfected, including scrubbing the sides of the tank to remove bacterial biofilm. An ultrafilter should be used distal to the storage tank.768, 793

Microbiologic sampling of dialysis fluids is recommended because gram-negative bacteria can proliferate rapidly in water and dialysate in hemodialysis systems; high levels of these organisms place patients at risk of pyrogenic reactions or healthcare-associated infection.643, 644, 768

Table 27. Factors Influencing Microbial Contamination in Hemodialysis Systems

Healthcare facilities are advised to sample dialysis fluids at least monthly using standard microbiological assay methods for waterborne microorganisms.750, 753, 759, 794 - 796 Water used to reprocess hemodialyzers for reuse on the same patient should also be tested for bacterial endotoxin on a monthly basis.789, 797 Information about water sampling methods for dialysis is provided in Appendix C.

Cross-contamination of dialysis machines and inadequate disinfection measures can facilitate the spread of waterborne organisms to patients. Steps should be taken to ensure that dialysis equipment is performing correctly and that all connectors, lines, and other components are specific for the equipment, in good repair, and properly in place. A recent outbreak of gram-negative bacteremias among dialysis patients was attributed to faulty valves in a drain port of the machine that allowed backflow of saline used to flush the dialyzer before patient use.798, 799 This backflow contaminated the drain priming connectors, which in turn contaminated the blood lines and exposed the patients to high concentrations of gram-negative bacteria. Environmental infection control in dialysis settings also includes low-level disinfection of housekeeping surfaces and spot decontamination of spills of blood (see the Environmental Services portion of Part I of this guideline for further information).

Peritoneal dialysis (PD), most commonly administered as continuous ambulatory peritoneal dialysis (CAPD) and continual cycling peritoneal dialysis (CCPD), is the third most common treatment for end-stage renal disease (ESRD) in the United States, accounting for 12% of all dialysis patients.800 Peritonitis is the most important complication of CAPD, with coagulase-negative staphylococci the most clinically significant causative organisms.801 Other organisms that have been found to produce peritonitis include Staphylococcus aureus, Mycobacterium fortuitum, M. mucogenicum, Stenotrophomonas maltophilia, Burkholderia cepacia, Corynebacterium jekeium, Candida spp., and other fungi.802 – 810

Substantial morbidity is associated with peritoneal dialysis infections. Removal of peritoneal dialysis catheters is usually required for treatment of peritonitis caused by fungi, NTM, or other bacteria that are not cleared within the first several days of effective antimicrobial treatment. Furthermore, recurrent episodes of peritonitis may lead to fibrosis and loss of the dialysis membrane.

Many reported episodes of peritonitis are associated with exit-site or tunneled catheter infections. Risk factors for the development of peritonitis in PD patients include: 1) under dialysis; 2) immune suppression; 3) prolonged antimicrobial treatment; 4) patient age [more infections in younger patients and older hospitalized patients]; 5) length of hospital stay; and 6) lower hypoalbuminemia.804, 811, 812 There has been some concern about infection risk related to the use of automated cyclers in both inpatient and outpatient settings. However, studies suggest that PD patients who use automated cyclers have much lower infection rates.813 One study noted that a closed-drainage system reduced the incidence of system-related peritonitis among intermittent peritoneal dialysis (IPD) patients from 3.6 to 1.5 cases/100 patient days.814 The association of peritonitis with management of spent dialysate fluids requires additional study. At present, it is prudent to ensure that the tip of the waste line is not submerged beneath the water level in a toilet or in a drain.

Microorganisms may be present in ice, ice-storage chests and ice-making machines. The two main sources of microorganisms in ice are the potable water from which it is made and a transferal of organisms from hands (Table 28).

Ice from contaminated ice machines has been associated with patient colonization, blood stream infections, pulmonary and gastrointestinal illnesses, and pseudoinfections.580, 581, 653, 654, 815, 816 Microorganisms in ice can secondarily contaminate clinical specimens and medical solutions which require cold temperatures for either transport or holding.579,

598 An outbreak of surgical site infections was interrupted when sterile ice was used in place of tap water ice to cool cardioplegia solutions.579

In a study comparing the microbial populations of hospital ice machines with organisms recovered from ice samples gathered from the community, samples from 27 hospital ice machines yielded low numbers (<10 CFU/mL) of a variety of potentially opportunistic microorganisms, mainly gram-negative bacilli.819 During the survey period, no healthcare-associated infections were attributed to the use of ice. Ice from community sources appeared to have higher levels of microbial contamination (75% - 95% of 194 samples had total heterotrophic plate counts <500 CFU/mL, with the proportion of positive cultures dependent on the incubation temperature) and showed evidence of fecal contamination from the source water.819 Thus, ice machines in health care are no more heavily contaminated compared to ice machines in the community. If the source water for ice in a healthcare facility is not fecally-contaminated, then ice from clean ice machines and chests should pose no special hazard for immunocompetent patients. Some waterborne bacteria found in ice could potentially be a risk to immunocompromised patients if they consume ice or drink beverages with ice. For example, Burkholderia cepacia in ice could present an infection risk for cystic fibrosis patients.819, 820 It may therefore be prudent to protect immunosuppressed and otherwise medically at-risk patients from exposure to tap water and ice potentially contaminated with opportunistic pathogens.9

Currently there are no microbiological standards for ice, ice-making machines, or ice storage equipment, although several investigators have suggested the need for such standards.819, 826 Culturing of ice machines is not routinely recommended but may be useful as part of an epidemiologic investigation.827 - 829 Sampling might also help determine the best schedule for cleaning open ice-storage chests. Recommendations for a regular program of maintenance and disinfection have been published.826 - 829 Healthcare facilities are advised to clean ice-storage chests at least monthly, with more frequent cleanings recommended for open chests. Portable ice chests and containers require cleaning and low-level disinfection before the addition of ice intended for consumption. Ice-making machines may require less frequent cleaning, but their maintenance is important to proper performance (Tables 29 and 30).

Hydrotherapy equipment (e.g., pools, whirlpools [jacuzzis], hot tubs, physiotherapy tanks) has traditionally been used to treat patients with medical conditions which include, but are not limited to burns,831, 832 septic ulcers, lesions, amputations,833 orthopedic impairments and injuries, arthritis,834 and more recently, kidney lithotripsy.630

Wound-care medicine is increasingly moving away from hydrotherapy, however, in favor of bedside pulsed-lavage therapy using sterile solutions for cleaning and irrigation.472, 835 - 838 Several episodes of healthcare-associated infections have been linked to use of hydroherapy equipment (Table 31). Potential routes of infection include incidental ingestion of the water, sprays and aerosols, and direct contact with

wounds and intact skin (folliculitis). Risk factors for infection include: 1) age and sex of the patient; 2) underlying medical conditions; 3) length of time spent in the hydrotherapy water; and 4) portals of entry.848

Infection control for hydrotherapy tanks, pools, or birthing tanks presents unusual challenges because indigenous microorganisms will always be present in the water during treatments. In addition, some studies have found free living amoebae (i.e., Naegleria lovaniensis) which are commonly found in association with N. fowleri in hospital hydrotherapy pools.849 Although there are instances when patients with wounds, burns, or other types of non-intact skin conditions receive treatment in hydrotherapy equipment, it is neither practical nor warranted to consider this equipment as "semi- critical" in accordance with the Spaulding classification.850 Microbial data to evaluate the risk of infection to patients using hydrotherapy pools or birthing tanks are insufficient. Nevertheless, healthcare facilities should maintain stringent cleaning and disinfection practices in accordance with the manufacturer’s instructions and with relevant scientific literature until data supporting more rigorous infection control measures become available.

Hydrotherapy tanks (e.g., whirlpools, Hubbard tanks) are shallow tanks constructed of stainless steel, Plexiglass, or tile. They are closed-cycle water systems with hydrojets to circulate, aerate, and agitate the water. The maximum water temperature range is 10°C - 40°C (50°F - 104°F). The warm water temperature, constant agitation and aeration, and design of the hydrotherapy tanks provide ideal conditions for bacterial proliferation if the equipment is not properly cleaned and maintained. Associated equipment (e.g., parallel bars, plinths, Hoyer lifts, wheelchairs) can also be potential reservoirs of microorganisms, depending on the materials used in these items (i.e., porous vs. non-porous materials) and the surfaces that may become wet during use. Patients with active skin colonizations and wound infections can serve as sources of contamination for the equipment and the water. Contamination from spilled tub water can extend to drains, floors, and walls.649 - 652

Healthcare-associated colonization or infection can result from exposure to endogenous sources of microorganisms (autoinoculation) or exogenous sources (via cross-contamination from other patients previously receiving treatment in the unit).

Although some facilities have used tub liners to minimize on environmental contamination of the tanks, the use of a tub liner does not eliminate the need for cleaning and disinfection. Draining these small pools and tanks after each patient use, thoroughly cleaning with a detergent, and disinfecting according to manufacturers’ instructions have been shown to reduce bacterial contamination levels in the water from 10 4 CFU/mL to <10 CFU/mL.851 The general recommendation is to maintain a chlorine residual of 15 ppm in the water prior to the patient’s therapy session (e.g., by adding 15 grams of calcium hypochlorite 70% [e.g., HTH®] per 100 gallons of water).851

A study of commercial and residential whirlpools found that superchlorination or draining, cleaning, disinfection, and refilling of whirlpools markedly reduced densities of Pseudomonas aeruginosa in the whirlpool water.852 The bacterial populations were rapidly replenished, however, when disinfectant concentrations dropped below recommended levels for recreational use (i.e., chlorine at 3.0 ppm or bromine at 6.0 ppm).

A few reports describe the addition of antiseptic chemicals to hydrotherapy tank water, especially for burn patient therapy.853 - 855 One small study showed a reduction in the number of Pseudomonas spp. and other gram-negative bacteria from both patients and equipment surfaces when chloramine-T ("chlorazene") is added to the water.856 Chloramine-T has not, however, been approved for water treatment in the United States.

Hydrotherapy pools typically serve large numbers of patients and are usually heated to 33°C - 37°C (91.4°F - 98.6°F). The temperature range is more narrow (35°C - 36°C [95°F - 96.8°F]) for pediatric and geriatric patient use.857 Because the size of hydrotherapy pools precludes draining after patient use, proper management is required to maintain the proper balance of water conditioning (i.e., alkalinity, hardness, temperature) and disinfection. The most widely used chemicals for disinfection of pools are chlorine and chlorine compounds -- calcium hypochlorite, sodium hypochlorite, lithium hypochlorite, chloroisocyanurates, and chlorine gas. Solid and liquid formulations of chlorine chemicals are the easiest and safest to use.858 Other halogenated compounds have also been used for pool water disinfection, albeit on a limited scale. Bromine, which forms bactericidal bromamines in the presence of ammonia, has limited use because it has been associated with contact dermatitis.859 Iodine does not bleach hair, swim suits, or cause eye irritation, but when introduced at proper concentrations, it will give water a greenish-yellowish cast.851

In practical terms, maintenance of large hydrotherapy pools, such as those used for exercise, is similar to that for indoor public pools (i.e., continuous filtration, chlorine residuals no less than 0.4 ppm, and pH between 7.2 -7.6).860, 861 Supply pipes and pumps also need to be maintained to eliminate these as possible reservoirs for waterborne organisms.862

Specific standards for chlorine residual and pH of the water are addressed in local and state regulations. Patients who are fecally-incontinent or who have draining wounds should refrain from using these pools until their condition improves.

The use of birthing tanks, jacuzzis, and whirlpools is a recent addition to obstetrical practice.863 Few studies on the potential risks associated with these pieces of equipment have been conducted. In one small study of 32 women, a newborn contracted a Pseudomonas infection, the strain of which was identical to the organism isolated from the tank water.864 Other studies have shown no significant increases in the rates of post-immersion infections among mothers and infants.865, 866

Because the water and the tub surfaces routinely become contaminated with the mother’s skin flora and blood during labor and delivery, birthing tanks and other tub equipment need to be drained after each patient use and the surfaces thoroughly cleaned and disinfected. Healthcare facilities are advised to follow the manufacturer’s instructions for selection of disinfection method and chemical germicide. Chlorine residuals for public whirlpools and jacuzzis ranges from 2 - 5 ppm.867 Use of an inflatable tub is an alternative solution, but this item must be cleaned and disinfected between patients if it is not considered as a single-use unit. A recent trend in health care is to use recreational tanks or jacuzzis as hydrotherapy equipment. Although such home equipment appears to be suitable for hydrotherapy, they are neither designed nor constructed to function in this capacity.

Additionally, manufacturers are generally not obligated to provide the healthcare facility with cleaning and disinfecting instructions appropriate for medical equipment use, and the U.S. Food & Drug Administration (FDA) does not evaluate recreational equipment. Healthcare facilities should therefore carefully evaluate this "off-label" use of home equipment before proceeding with a purchase.

The automated endoscopic reprocessor (AER) is classified by the FDA as an accessory for the flexible fiberoptic endoscope.630 A properly operating AER can provide a more consistent, reliable method of decontaminating and terminal reprocessing for endoscopes between patient procedures than manual reprocessing methods alone.868, 869 An endoscope is generally subjected to high-level disinfection using a liquid chemical sterilant. The optimal rinse fluid for a disinfected endoscope would be sterile water, since the instrument is a semi-critical device.3 Sterile water, however, is expensive and difficult to produce in sufficient quantities and with adequate quality assurance for instrument rinsing in an AER. Therefore, one option that is used for AERs is rinse water which has been passed through filters with a pore size of 0.1 - 0.2 µm (i.e., to render the water "bacteria-free"). These filters are usually located in the water line at or near the port where the mains water enters the equipment.

Two general situations have linked water to contamination of flexible fiberoptic endoscopes: 1) rinsing a disinfected endoscope with unfiltered tap water, followed by storage of the instrument without drying out the internal channels; and 2) contamination of AERs from tap water inadvertently introduced into the equipment. In the latter instance, the machine’s water reservoirs and fluid circuitry become contaminated with waterborne, heterotrophic bacteria (e.g., Pseudomonas aeruginosa, NTM) which can survive and persist in biofilms attached to these components.870 – 873

Colonization of the reservoirs and water lines of the AER becomes a problem if the required cleaning, disinfection, and maintenance are not performed on the equipment as recommended by the manufacturer.872 - 874 Use of the 0.1 - 0.2 µm filter in the water line helps to keep bacterial contamination to a minimum,869, 873, 875 but filters may fail and allow bacteria to pass on through.876, 877

Filters also require maintenance for proper performance.875, 878 Increasing attention to the proper disinfection of the connectors that hook the instrument to the AER may help to further reduce the potential for contaminating endoscopes during reprocessing.879

Studies have linked deficiencies in endoscope cleaning and/or disinfecting processes to the incidence of post-endoscopic adverse outcomes.880 - 883 Several clusters have been traced to AERs of older designs, and these were associated with water quality.870 - 872, 884 Regardless of whether manual or automated terminal reprocessing is used for endoscopes, the internal channels of the instrument must be dried before storage. The presence of residual moisture in the internal channels encourages the proliferation of waterborne microorganisms, some of which may be potentially pathogenic.

Using 70% isopropyl alcohol to flush the internal channels, followed by forced air drying of these channels and hanging the endoscope vertically in a protected cabinet will ensure internal drying of the endoscope and lessen the potential for proliferation of waterborne microorganisms, whether they originate from the disinfector water or from residual contamination from the previous patient.873, 874, 881, 885 This is part of the worldwide standard process for successful endoscope reprocessing.886

An additional problem with waterborne microbial contamination of AERs centers on increased microbial resistance to sterilants such as alkaline glutaraldehyde.874, 887 Opportunistic waterborne microorganisms (e.g., Mycobacterium chelonae, Methylobacterium spp.) have been associated with pseudo-outbreaks, colonization, and infection in clinical settings such as bronchoscopy.874, 887, 888 The problem of increasing microbial resistance to glutaraldehyde has been attributed to improper use of the disinfectant in the equipment which allows the dilution of glutaraldehyde to fall below the manufacturer’s recommended minimal use concentration of 1.5%.887

Dental unit water lines (DUWLs) consist of small-bore plastic tubing that delivers water used for general, non-surgical irrigation and as a coolant to dental handpieces, sonic and ultrasonic scalers, and air-water syringes; municipal tap water is the source water for these lines. The presence of biofilms of waterborne bacteria and fungi (e.g., Legionella spp., Pseudomonas aeruginosa, NTM) in DUWLs has been well established.613, 662, 663, 889, 890 Biofilms continually release planktonic microorganisms into the water, the titers of which can exceed 1x10 6 CFU/mL.662 To date, however, scientific evidence indicates there is little risk of significant adverse health effects among immunocompetent persons due to contact with water from a dental unit. Nonetheless, exposing patients or dental personnel to water of uncertain microbiological quality is not consistent with universally accepted infection control principles.891

In 1993, the CDC issued guidelines relative to water quality in a dental setting. These guidelines recommend that all dental instruments that use water (including high-speed handpieces) should be run to discharge water for 20-30 seconds after each patient and for several minutes before the start of each clinic day.892 Although these guidelines are designed to help reduce the number of microorganisms present in treatment water, they do not address the issue of reducing or preventing biofilm formation in the waterlines.

The numbers of microorganisms in water used as coolant or irrigant for non-surgical dental treatment should be as low as reasonably achievable and, at a minimum, should meet nationally recognized standards for safe drinking water.893

There is minimal evidence that water that meets drinking water standards poses a health hazard for immunocompetent persons. The EPA, the American Public Health Association (APHA), and the American Water Works Association (AWWA) have set a maximum limit for aerobic, heterotrophic, mesophilic bacteria in drinking water at 500 CFU/mL.894,

895 This standard is achievable today, given improvements in water line technology. An upcoming revision to the 1993 CDC dental infection control guidelines may consider a standard such as that for dialysis water quality (i.e., < 200CFU/mL) be adopted for DUWLs. Dentists should consult with the manufacturer of their dental unit to determine the best equipment and method for maintaining and monitoring good water quality.891

As in previous CDC guidelines, each recommendation is categorized on the basis of existing scientific data, theoretical rationale, applicability, and possible economic impact. The HICPAC system for categorizing recommendations has been modified to include a designation for engineering standards and actions required by state or federal regulations. Some of the recommendation statements of this guideline are largely derived from experience gained from situations that cannot be easily studied (e.g., floods). Guidelines and standards published by the American Institute of Architects (AIA) and the American Society of Heating, Refrigerating, and Air-conditioning Engineers (ASHRAE) form the basis of many of the recommendations. These publications include the AIA Guidelines for Design and Construction of Hospitals and Health Care Facilities 120 and the ASHRAE guidelines entitled Ventilation for Acceptable Indoor Air Quality and Minimizing the Risk of Legionellosis Associated with Building Water Systems.210, 637 Standards for a variety of engineered systems (e.g., air handling systems, cooling towers) are promulgated by ASHRAE based on engineer member input and CDC consultation.

Recommendations are categorized according to the following designations:

Category IA - Strongly recommended for implementation and strongly supported by well-designed experimental, clinical, or epidemiological studies.

Category IB - Strongly recommended for implementation and supported by some experimental, clinical, or epidemiological studies and a strong theoretical rationale.

Category IC - Required by state or federal regulations, rules, or standards.

Category II - Suggested for implementation and supported by suggestive clinical or epidemiological studies or a theoretical rationale.

No recommendation - Unresolved issue. Practices for which insufficient evidence or no consensus regarding efficacy exists.

C. Recommendations

2-1.1 Practice consistent handwashing/hand hygiene to prevent the spread of waterborne pathogens; use barrier precautions (e.g., gloves) in accordance with current guidelines.6, 444, 555, 564, 570 Category IA

2-1.2 Eliminate contaminated environmental reservoirs (e.g., equipment, solutions) whenever possible.444, 445 Category IB

2-1.3 Clean and disinfect sinks and wash basins on a regular basis. Category II

2-1.4 Rule out contamination from water whenever waterborne microorganisms, especially NTM, are isolated from clinical specimens collected aseptically from sterile sites or if post-procedural infection or colonization occurs after use of tap water in patient care.597 - 599 , 604 Category IB

2-2.1 Maintain hot water temperature at the outlet at the highest temperature allowable by state regulations or codes, preferably >51°C (>124°F), and maintain cold water temperature at <20°C (<68°F).3, 637 Category IC

2-2.2 If the hot water temperature can be maintained at >51°C (>124°F), install preset thermostatic valves in point-of-use fixtures to help minimize the risk of scalding. Category II

2-2.3 When state regulations or codes do not allow hot water temperatures >43°C (>110°F), follow alternative preventive measures to minimize the growth of Legionella spp. in water systems. Category II

2-2.3.a Periodically increase the hot water temperature to >66°C (>150°F) at the point of use (with thermostatic mixing valves present). Category II

2-2.3.b Alternatively, if the building cannot be retrofitted with thermostatic mixing valves, chlorinate the water and then flush it through the system.637, 678, 679 Category II

2-2.4 Maintain constant recirculation in hot-water distribution systems serving patient-care areas.120 Category IC

2-2.5 When water disruptions occur, use the following infection control measures:

2-2.5.a Prepare a contingency plan to estimate water demands for the entire facility; Category IC

2-2.5.b Post signs advising patients, families, staff, and visitors not to drink tap water until the system is cleared for use by the facility engineer. Category IC

2-2.5.c When the system function is restored:

i Thoroughly flush the system with water at ambient temperatures, or

ii Use high-temperature water flushing or chlorination.637 Category IC.107

iii Flush and restart equipment and fixtures according to manufacturers’ instructions. Category IC

2-2.6 When corrective decontamination of the hot water system is necessary after a disruption in service or a cross-connection with sewer lines has occurred:

2-2.6.a Decontaminate the system when the fewest occupants are present in the building (e.g., nights, weekends).3 Category II

2-2.6.b If using high-temperature decontamination, raise the hot-water temperature to 71°C -77°C (160°F -170° F), progressively flushing each outlet; flush the system for a minimum of 5 minutes.3, 637 Category IC

2-2.6.c If using chlorination, add enough chlorine, preferably overnight, to achieve a free chlorine residual of >2 mg/L (>2 ppm) throughout the system.637 Category IC

2-2.7 Adhere to any "boil water" advisory issued by the municipal water utility. Category IC

2-2.7.a Alert patients, families, staff, and visitors not to consume water from drinking fountains, ice, or drinks made from municipal tap water while the advisory is in effect unless the water has been disinfected by bringing to a rolling boil for 1 minute.619 Category IC

2-2.7.b After the advisory is lifted, run faucets and drinking fountains at full flow for several minutes; maintain a high level of surveillance for waterborne disease among patients.619 Category IC

2-2.7.c Change the pre-treatment filter and disinfect the dialysis water system to prevent colonization of the RO membrane and downstream microbial contamination.687 Category IC

2-2.7.d Run water softeners through a regeneration cycle to restore their capacity and function. Category IC

2-2.7.e Inspect water storage tanks to determine if they need to be drained, disinfected, and refilled. Category IC

2-2.8 Implement procedures to manage a sewage system failure or flooding:

2-2.8.a Develop a contingency plan in accordance with JCAHO requirements.686 Category IC

2-2.8.b Relocate patients and clean/sterile supplies from affected areas, and close off these areas during clean-up procedures. Category IC

2-2.8.c Ensure that the sewage system is fully functional before beginning remediation so that contaminated solids and standing water can be removed. Category IC

2-2.8.d If hard-surface equipment, floors, and walls remain in good repair, allow them to dry out; clean with detergent according to standard cleaning procedures. Category IC

2-2.8.e Remove absorbent structural items (e.g., carpeting, wallboard, wallpaper) and cloth furnishings if they cannot be easily and thoroughly cleaned and dried within 72 hours; replace with new materials as soon as the underlying structure is declared thoroughly dry by the hospital engineer. Category IC

2-2.8.f Clean wood furniture and materials (if still in good repair); allow them to dry thoroughly before restoring varnish or other surface coatings. Category IC

2-2.8.g Contain dust and debris during remediation and repair as per recommendation (1-2.7.e). Category IC

2-3.1 Use proper decontamination strategies as needed to eliminate legionellae from the healthcare facility’s hot water supply.730 Category IB

2-3.1.a When using a pulse (one time) decontamination method, superheat the water by flushing each outlet for >5 minutes with water at 71°C - 77°C (160°F - 170°F) or hyperchlorinate the system by flushing all outlets for >5 minutes with water containing >10 mg/L (>10 ppm) free residual chlorine.637, 679, 681, 690, 728 Category IB

2-3.1.b After a pulse treatment, maintain water temperatures at the outlet as per the recommendation (2-2.1) wherever practical and permitted by state codes, or chlorinate heated water to achieve 1 - 2 mg/L (1 – 2 ppm) free residual chlorine at the tap.26, 436, 637, 677, 692, 693 Category IC

2-3.1.c Install preset thermostatic mixing valves in point-of-use fixtures to minimize the risk of scalding or post warning signs at each outlet to alert patients, visitors, and staff about the potential for scalding.

2-3.2 No recommendation for treating water with ozone, UV light, heavy-metal ions, or monochloramines.694 – 710 Unresolved issue

2-3.3 Implement strategies for preventing Legionnaires’ disease.

2-3.3.a Establish a surveillance process to detect healthcare-associated Legionnaires’ disease:

i Inform healthcare personnel (e.g., infection control, physicians, patient-care staff, engineering) about the potential for Legionnaires’ disease to occur and measures to prevent and control healthcare-associated legionellosis.436, 723 Category IB

ii Establish mechanisms to provide clinicians with laboratory tests (i.e., culture, urine antigen, DFA serology) for the diagnosis of Legionnaires’ disease.3, 430 Category II

iii Maintain a high index of suspicion for healthcare-associated Legionnaires’ disease, especially in high-risk patients (e.g., persons with chronic underlying disease, immunocompromised patients, persons >65 of age).3, 377, 385, 416, 422 - 424, 431, 434, 436 Category II

2-3.3.b No recommendation on routine culturing of water systems in healthcare facilities that do not have patient-care areas (i.e., transplant units) for persons at high risk for Legionella infection.26, 434, 675, 677, 681, 711, 717 Unresolved issue

2-3.3.c If one case of laboratory-confirmed, definite healthcare-associated Legionnaires’ disease is identified, OR if two or more cases of laboratory-confirmed, possible healthcare-associated Legionnaires’ disease occur during a 6-month period, report the cases to the state and local health departments, and conduct an epidemiologic investigation. Category II

i If a case occurs in a severely immunocompromised patient, or if severely immunocompromised patients are present in high-risk areas of the hospital (e.g., transplant units), conduct a combined epidemiologic and environmental investigation to determine the source of Legionella spp. Category II

ii If the facility does not treat severely immunocompromised patients, conduct a retrospective review of microbiologic, serologic, and postmortem data to look for previously unidentified cases of healthcare-associated Legionnaires’ disease, and begin intensive prospective surveillance for additional cases. Category II

2-3.3.d If there is no evidence of continued healthcare-associated transmission, continue intensive prospective surveillance for at least 2 months after the initiation of surveillance. Category II

2-3.3.e If there is evidence of continued healthcare-associated transmission, conduct an environmental investigation to determine the source of Legionella spp. Category IB

i Collect water samples from potential sources of aerosolized water according to the methods described in Appendix C. Category II

ii Save and subtype isolates of Legionella spp. obtained from patients and the environment.388 - 396, 727, 728 Category IB

2-3.3.f If a source is not identified, continue surveillance for new cases for at least 2 months; depending on the scope of the outbreak, either defer decontamination pending identification of the source of Legionella spp., or proceed with decontamination of the hospital's water distribution system, with special attention to areas involved in the outbreak. Category II

2-3.3.g If a source is identified, promptly institute water system decontamination measures as per recommendation (2-3.1).730 Category IB

2-3.3.h Clean hot-water storage tanks and water heaters to remove accumulated scale and sediment.398 Category II

2-3.3.i No recommendation for the removal of faucet aerators in areas for immunocompetent patients. Unresolved issue

2-3.4 Assess the efficacy of implemented measures in reducing or eliminating Legionella spp. by collecting specimens for culture at 2-week intervals for 3 months. Category II

2-3.4.a If Legionella spp. are not detected in cultures during 3 months of monitoring at 2-week intervals, collect cultures monthly for another 3 months. Category II

2-3.4.b If Legionella spp. are detected in one or more cultures, reassess the control measures, modify them accordingly, and repeat the decontamination procedures, with possible approaches including the intensive use of the same technique used for initial decontamination or a combination of superheating and hyperchlorination. Category II

2-3.5 Keep adequate records of all infection-control measures and environmental test results for potable water systems. Category II

2-3.6 Strategies for preventing Legionnaires’ disease among immunosuppressed patients housed in facilities with transplant units include:

2-3.6.a Maintain a high index of suspicion for legionellosis in transplant patients even when environmental surveillance cultures do not yield legionellae.429, 430 Category II

2-3.6.b Depending on state regulations on potable water temperature in public buildings,691 hospitals housing patients at high risk for healthcare-associated legionellosis should either maintain potable water at the outlet at >51°C [>124°F] or <20°C [<68°F] or chlorinate heated water to achieve 1 - 2 mg/L [1 - 2 ppm] of free residual chlorine at the tap.26, 436, 637, 677 - 679, 692, 693 Category II

2-3.6.c When Legionella spp. are not detectable in unit water, remove, clean, and disinfect shower heads and tap aerators in high-risk patient-care areas monthly using a chlorine bleach solution (i.e., 1:100 dilution of bleach).637, 709 Category II

2-3.6.d Facilities with organ transplant units should consider conducting periodic environmental surveillance (culturing) for legionellae in water samples as part of an overall strategy to prevent Legionnaires’ disease, the goal of which in these instances should be to maintain water systems with no detectable organisms.9, 430 Category II

2-3.6.e No recommendation on the optimal methodology (i.e., frequency or number of sites) for environmental surveillance cultures in transplant units. Unresolved issue

2-3.6.f If Legionella spp. are detected in the water of a transplant unit, the following should be done until Legionella spp. are no longer detected by culture:

i Decontaminate the water supply as per recommendation (2-3.1).3, 9, 637 Category IB

ii Restrict severely immunosuppressed patients from taking showers.9, 411 Category IB

iii Use water that is not contaminated with Legionella spp. for HSCT patients’ sponge baths.9 Category IB

iv Provide patients with sterile water for tooth brushing, drinking, and for flushing nasogastric tubing during legionellosis outbreaks.9, 411 Category IB

v Remove aerators from faucets and avoid use of tap water from faucets.9 Category II

2-3.6.g Do not use large-volume room air humidifiers that create aerosols (e.g., by Venturi principle, ultrasound, or spinning disk) unless they are subjected to high-level disinfection and filled only with sterile water.3, 9 Category II

2-4.1 When planning construction of new healthcare facilities, locate cooling towers so that the drift is directed away from the air-intake system, and design the towers to minimize the volume of aerosol drift.390, 637, 747 Category IC

2-4.2 Implement infection control procedures for operational cooling towers.

2-4.2.a Install drift eliminators.390, 637, 745 Category IC

2-4.2.b Use an effective biocide on a regular basis. Category IC

2-4.2.c Maintain towers according to manufacturers’ recommendations, and keep detailed maintenance and infection control records, including environmental test results from legionellosis outbreak investigations.637 Category IC

2-4.2.d If cooling towers or evaporative condensers are implicated in healthcare-associated legionellosis, decontaminate the cooling-tower system.390, 391, 747, 748 Category IB

2-5.1 Adhere to current AAMI standards for quality assurance performance of devices and equipment used to treat, store, and distribute water in hemodialysis centers (both acute and maintenance settings) and for the preparation of concentrates and dialysate.749, 750 Category IA

2-5.2 No recommendation on whether more stringent requirements for water quality should be imposed in hemofiltration and hemodiafiltration. Unresolved issue

2-5.3 Conduct microbiological testing specific to water in dialysis settings. Category IA

2-5.3.a Perform bacteriologic assays of water and dialysis fluids at least once a month and during outbreaks using standard quantitative methods.749, 750, 794, 795 Category IA

i Assay for heterotrophic, mesophilic bacteria.

ii Do not use a nutrient-rich media such as blood agar or chocolate agar.

2-5.3.b In conjunction with microbiological testing, perform endotoxin testing, especially on samples from water used to reprocess hemodialyzers.751, 752, 789 Category IA.110

2-5.3.c Ensure that water does not exceed the limits for microbial counts and endotoxin concentrations outlined in Table 26. 749 - 752 Category IA

2-5.4 Disinfect water distribution systems in dialysis settings at least weekly.749, 750 Category IA

2-5.5 Design and engineer water systems in dialysis settings so that they are free of joints, dead-end pipes, and unused branches and taps that can harbor bacteria.760 Category IC

2-5.6 Do not use storage tanks in dialysis systems unless they are routinely drained, disinfected, and have an ultrafilter (membrane filter with a pore size sufficient to remove small particles and molecules >1 kilodalton in size) installed in the water line distal to the storage tank.749, 750 Category IC

2-6.1 Do not handle ice directly by hand, and wash hands before obtaining ice. Category II

2-6.2 Use a smooth-surface ice scoop to dispense ice; keep the ice scoop on a chain short enough so the scoop cannot touch the floor, or keep the scoop on a clean, hard surface when not in use.649, 823 Category II

2-6.3 Do not store pharmaceuticals or medical solutions on ice intended for consumption; use sterile ice to keep medical solutions cold, or use equipment specifically manufactured for this purpose.578, 823 Category IB

2-6.4 Limit access to ice-storage chests, and keep the container doors closed except when removing ice.823 Category II

2-6.5 Clean and disinfect ice-storage chests on a regular basis. Category II

2-6.5.a Follow manufacturers’ instructions for cleaning and frequency of cleaning. Category II

2-6.5.b If instructions are not available, use a general cleaning/disinfecting regimen (Table 29).823 Category II

2-6.6 To ensure performance and maintain infection control, perform regular maintenance of ice machines according to manufacturers’ instructions or, in the absence of manufacturers’ instructions clean, disinfect, and maintain ice machines on a regular basis using a general approach as outlined in Table 30. 823 Category II

2-6.7 Conduct microbiologic sampling of ice, ice chests, and ice-making machines if indicated for an epidemiologic investigation.821 - 823 Category IB

2-7.1 Drain and clean hydrotherapy equipment (e.g., Hubbard tanks, tubs, whirlpools, jacuzzis, birthing tanks) after each patient, and disinfect equipment surfaces and components in accordance with manufacturers’ instructions and relevant scientific literature. Category IC

2-7.2 In the absence of manufacturers’ recommendations for water treatment, add disinfectant to the water:

2-7.2.a Maintain a 15-ppm chlorine residual in the water of small hydrotherapy tanks, Hubbard tanks, and tubs.847 Category II

2-7.2.b Maintain a 2- to 5-ppm chlorine residual in the water of whirlpools and jacuzzis.863 Category II

2-7.3 Clean and disinfect hydrotherapy equipment after using tub liners. Category II

2-7.4 Clean and disinfect inflatable tubs unless they are used as single-use equipment. Category II

2-7.5 No recommendation on the use of antiseptic chemicals (e.g., chloramine-T) in the water during hydrotherapy sessions. Unresolved issue

2-7.6 Use appropriate infection control measures for large hydrotherapy pools:

2-7.6.a Conduct a risk assessment of patients prior to their use of the pool, deferring patients with draining wounds or fecal incontinence from pool use until their condition resolves. Category II

2-7.6.b Use pH and chlorine residual levels appropriate for an indoor pool as provided by local and state health agencies. Category IC

2-7.7 No recommendation on the use in health care of equipment manufactured for home or recreational use. Unresolved issue

2-8.1 Clean, disinfect, and maintain automated endoscope reprocessor (AER) equipment according to manufacturers’ instructions and relevant scientific literature.868 - 870 Category IB

2-8.1.a Rinse disinfected endoscopes in water that is bacteria-free at a minimum; if sterile water is not available or practical, use bacteriologically-filtered water (water filtered through 0.1- to 0.2-µm filters).865, 870, 871 Category IB

2-8.1.b Flush reprocessed endoscopes with 70% alcohol, followed by forced-air treatment to ensure adequate drying of the internal channels and to prevent the formation of biofilms.876, 880, 882 Category IB

2-8.2 Take precautions to prevent waterborne contamination of dental unit water lines and instruments:

2-8.3.a Flush all dental instruments that use water, including high-speed handpieces for several minutes before the start of each clinic day.892 Category II

2-8.3.b Ensure that water in dental unit water lines meets nationally recognized drinking water standards (<500 CFU/mL for heterotrophic plate count) at a minimum.891 - 893 Category IC

2-8.3.c Consult with dental water line manufacturers to determine suitable methods and equipment to obtain good water quality.892 Category II

See PDF File

This glossary contains many of the terms used in this guideline, as well as others that are encountered frequently when implementing these control measures. The definitions are generally not dictionary definitions, but are those most applicable to environmental infection control situations.

Acceptable indoor air quality - air in which there are no known contaminants at harmful concentrations as determined by knowledgeble authorities and with which a substantial majority (> 80%) of the people exposed do not express dissatisfaction.

ACGIH - American Conference of Governmental Industrial Hygienists.

Aerosol - particles of respirable size generated by both humans and environmental sources and that have the capability of remaining viable and airborne for extended periods in the indoor environment.

AIA - American Institute of Architects: professional group responsible for publishing the "Guidelines for Design and Construction of Hospitals and Healthcare Facilities," a consensus document for design and construction of health care facilities endorsed by the U.S. Department of Health and Human Services, healthcare professionals, and professional organizations.

Air changes per hour (ACH) - the ratio of the volume of air flowing through a space in a certain period of time (i.e., the airflow rate) to the volume of that space (i.e., the room volume); this ratio is usually expressed as the number of air changes per hour (ACH).

Air mixing - the degree to which air supplied to a room mixes with the air already in the room, usually expressed as a mixing factor. This factor varies from 1 (for perfect mixing) to 10 (for poor mixing), and it is used as a multiplier to determine the actual airflow required (i.e., the recommended ACH multiplied by the mixing factor equals the actual ACH required).

Airborne transmission - a means of spreading infection when airborne droplet nuclei (small particle residue of evaporated droplets < 5 µm in size containing microorganisms that remain suspended in air for long periods of time) are inhaled by the susceptible host.

Air-cleaning system - a device or combination of devices applied to reduce the concentration of airborne contaminants (i.e., microorganisms, dusts, fumes, aerosols, other particulate matter, gases).

Air conditioning - the process of treating air to meet the requirements of a conditioned space by controlling its temperature, humidity, cleanliness, and distribution.

Allogeneic - non-twin, non-self; refers to transplanted tissue from a donor closely matched to a recipient but not related to that person.

Ambient air - the air surrounding an object.

Anemometer - a flow meter which measures the wind force and velocity of air. An anemometer is often used as a means of determining the volume of air being drawn into an air sampler.

Anteroom - a small room leading from a corridor into an isolation room: this room can act as an airlock, preventing the escape of contaminants from the isolation room into the corridor.

ASHE - American Society of Hospital Engineers, an association affiliated with the American Hospital Association.

ASHRAE - American Society of Heating, Refrigerating, and Air Conditioning Engineers Inc. The engineering counterpart of AIA.

Autologous - self; refers to transplanted tissue whose source is the same as the recipient, or a twin.

Automated cycler - a machine used during peritoneal dialysis which pumps fluid into and out of the patient while he/she sleeps.

Biochemical oxygen demand (BOD) - a measure of the amount of oxygen removed from aquatic environments by aerobic microorganisms for their metabolic requirements. Measurement of BOD is used to determine the level of organic pollution of a stream or lake. The greater the BOD, the greater the degree of water pollution. Also referred to as Biological Oxygen Demand (BOD).

Biological oxygen demand (BOD) - as this pertains to water quality, an indirect measure of the concentration of biologically degradable material present in organic wastes. It usually reflects the amount of oxygen consumed in five days by biological processes breaking down organic waste (BOD5).

Biosafety level - a combination of microbiological practices, laboratory facilities, and safety equipment determined to be sufficient to reduce or prevent occupational exposures of laboratory personnel to the microbiological agents they work with. There are four biosafety levels based on the hazards associated with the various microbiological agents.

BOD5 - the amount of dissolved oxygen consumed in five days by biological processes breaking down organic matter.

Bonneting - a floor cleaning method for either carpeted or hard surface floors which uses a circular motion of a large, fibrous disc to lift soil and dust from the surface and remove it.

Capped spur - a pipe leading from the water recirculating system to an outlet that has been closed off ("capped"). A capped spur cannot be flushed, and it might not be noticed unless the surrounding wall is removed.

CFU/m 3 - colony forming units per cubic meter (of air)

Chlamydospores - thick-walled, typically spherical or ovoid resting spores produced (asexually) by certain types of fungi from cells of the somatic hyphae.

Chloramines - compounds containing nitrogen, hydrogen, and chlorine, formed by the reaction between hypochlorous acid (HOCl) and ammonia (NH3) and/or organic amines in water. The formation of chloramines in drinking water treatment extends the disinfecting power of chlorine. Also referred to as Combined Available Chlorine.

Cleaning - the removal of visible soil and organic contamination from a device or surface, using either the physical action of scrubbing with a surfactant or detergent and water, or an energy-based process (e.g., ultrasonic cleaners) with appropriate chemical agents.

Coagulation-flocculation - coagulation is the clumping of particles which results in the settling of impurities. It may be induced by coagulants such as lime, alum, and iron salts. Flocculation in water and wastewater treatment is the agglomeration or clustering of colloidal and finely divided suspended matter after coagulation by gentle stirring by either mechanical or hydraulic means such that they can be separated from water or sewage.

Commissioning (a room) - testing a system or device to ensure that it meets the pre-use pecifications as indicated by the manufacturer or predetermined standard, or air sampling in a room to establish a pre-occupancy baseline standard of microbial or particulate contamination. Also referred to as benchmarking at 25°C.

Conidia - asexual spores of fungi borne externally.

Conidiophores - specialized hyphae that bear conidia in fungi.

Conditioned space - that part of a building that is heated or cooled, or both, for the comfort of the occupants.

Contaminant - an unwanted airborne constituent that may reduce acceptibility of the air.

Convection - the transfer of heat or other atmospheric properties within the atmosphere or in the airspace of an enclosure by the circulation of currents from one region to another, especially by such motion directed upward.

Cooling tower - a structure engineered to receive accumulated heat from ventilation systems and equipment and transfer this heat to water, which then releases the stored heat to the atmosphere through evaporative cooling.

Critical item (medical instrument) - medical instruments or devices that contact normally sterile areas of the body or enter the vascular system. There is a high risk of infection from these devices if these are microbiologically contaminated prior to use; these devices must be sterile before use.

Dead legs - areas in the water system where water stagnates. A dead leg is a pipe, or spur, leading from the water recirculating system to an outlet that is used infrequently, resulting in inadequate flow of heat or chlorine from the recirculating system to the outlet.

Deionization - removal of ions from water by exchange with other ions associated with fixed charges on a resin bed. Cations are usually removed and H + ions are exchanged; OH - ions are exchanged for anions.

Detritis - particulate matter produced by or remaining after the wearing away or disintegration of a substance or tissue.

Dew point - the temperature at which a gas or vapor condenses to form a liquid; the point at which moisture begins to condense out of the air. At dew point, air is cooled to the point where it is at 100% relative humidity or saturation.

Dialysate - the aqueous electrolyte solution, usually containing dextrose, used to make a concentration gradient between the solution and blood in the hemodialyzer (dialyzer).

Dialyzer - a device that consists of two compartments (blood and dialysate) separated by a semipermeable membrane. A dialyzer is usually referred to as an artificial kidney.

Diffuser - the grille plate which disperses the air stream coming into the conditioned air space.

Direct transmission - involves direct body surface-to-body surface contact and physical transfer of microorganisms between a susceptible host and an infected/colonized person, orc exposure to cloud of infectious particles within 3 feet; particles are >5 µm in size.

Disability - as defined by the Americans with Disabilities Act, is any physical or mental impairment that substantially limits one or more major life activities, including but not limited to walking, talking, seeing, breathing, hearing, or caring for oneself.

Disinfection - a generally less lethal process of microbial inactivation (compared to sterilization) which eliminates virtually all recognized pathogenic microorganisms but not necessarily all microbial forms (e.g., bacterial spores).

Drain pans - collect water as air and steam result in condensation.

Drift - circulating water lost from the cooling tower as liquid droplets entrained in the exhaust air stream (i.e., exhaust aerosols from a cooling tower).

Drift eliminators - an assembly of baffles or labyrinth passages through which the air passes prior to its exit from the cooling tower, for the purpose of removing entrained water droplets from the exhaust air.

Droplets - particles of moisture, such as are generated when a person coughs or sneezes, or when water is converted to a fine mist by a device such as an aerator or shower head. Intermediate in size between drops and droplet nuclei, these particles, although they may still contain infectious microorganisms, tend to quickly settle out from the air so that any risk of disease transmission is generally limited to persons in close proximity to the droplet source.

Droplet nuclei - sufficiently small particles (1 - 5µm in diameter) that can remain airborne indefinitely and cause infection when a susceptible person is exposed at or beyond 3 feet of particle source.

Dual duct system - an HVAC system that consists of parallel ducts that produce a cold air stream in one and a hot air stream in the other.

Dust - an air suspension of particles (aerosol) of any solid material, usually with particle sizes < 100 µm in diameter.

Dust spot test - a procedure which uses atmospheric air or a defined dust to measure a filter’s ability to remove particles. A photometer is used to measure air samples on either side of the filter, and the difference is expressed as a percentage of particles removed.

Effective leakage area - the area through which air can enter or leave the room. This does not include supply, return, or exhaust ducts. The smaller the effective leakage area, the better isolated the room.

Endotoxin - the lipopolysaccharides of gram-negative bacteria, the toxic character of which resides in the lipid portion. Endotoxins generally produce pyrogenic reactions in persons exposed to these bacterial components.

Enveloped virus - a virus whose outer surface is derived from a membrane of the host cell (either nuclear or outer membrane) during the budding phase of the maturation process. This membrane-derived material contains lipids, which makes these viruses sensitive to the action of chemical germicides.

Evaporative condenser - a wet-type, heat-rejection unit that produces large volumes of aerosols during the process of removing heat from conditioned space air.

Exhaust air - air removed from a space and not reused therein.

Exposure - the condition of being subjected to something (e.g., infectious agents) that could have a harmful effect.

Fastidious - having complex nutritional requirements for growth, as in microorganisms.

Fill - that portion of a cooling tower which makes up its primary heat transfer surface. Fill is alternatively known as "packing."

Finished water - treated, or potable water.

Fixed room-air HEPA recirculation systems - nonmobile devices or systems that remove airborne contaminants by recirculating air through a HEPA filter. These may be built into the room and permanently ducted or may be mounted to the wall or ceiling within the room. In either situation, they are fixed in place and are not easily movable.

Fomites - an inanimate object that may be contaminated with microorganisms and serve in their transmission.

Free, available chlorine - the term applied to the three forms of chlorine that may be found in solution (Cl2 , OCl - , and HOCl).

Germicide - a chemical that destroys microorganisms. Germicides may be used to inactivate microorganisms in or on living tissue (antiseptics) or on environmental surfaces (disinfectants).

Healthcare-associated - an outcome, usually an infection, that occurs in any healthcare facility as a result of medical care. The term "healthcare-associated" replaces "nosocomial," the latter term being limited to adverse infectious outcomes occurring in hospitals only.

Hemodiafiltration - a form of renal replacement therapy in which waste solutes in the patient’s blood are removed by both diffusion and convection through a high-flux membrane.

Hemodialysis - a treatment for renal replacement therapy in which waste solutes in the patient’s blood are removed by diffusion and/or convection through the semi-permeable membrane of an artificial kidney or dialyzer.

Hemofiltration - cleansing of waste products or other toxins from the blood by convection across a semi-permeable high-flux membrane where fluid balance is maintained by infusion of sterile, pyrogen-free substitution fluid pre- or post-hemodialyzer.

HEPA filter - High Efficiency Particulate Air filters capable of removing 99.97% of particles > 0.3 µm in diameter and may assist in controlling the transmission of airborne disease agents. These filters may be used in ventilation systems to remove particles from the air or in personal respirators to filter air before it is inhaled by the person wearing the respirator. The use of HEPA filters in ventilation systems requires expertise in installation and maintenance. To test this type of filter, 0.3 µm particles of dioctylphthalate (DOP) are drawn through the filter. Efficiency is calculated by comparing the downstream and upstream particle counts. The optimal HEPA filter allows only three particles to pass through for every 10,000 particles that are fed to the filter.

Heterotrophic (heterotroph) - that which requires some nutrient components from exogenous sources. Heterotrophic bacteria cannot synthesize all of their metabolites and therefore require certain nutrients from other sources.

High efficiency filter - a filter with a particle-removal efficiency of 90% - 95%.

High flux - type of dialyzer or hemodialysis treatment in which large molecules (>8,000 daltons [e.g., $2 microglobulin]) are removed.

High-level disinfection - a disinfection process which inactivates vegetative bacteria, mycobacteria, fungi, and viruses, but not necessarily high numbers of bacterial spores.

Housekeeping surfaces - environmental surfaces (e.g., floors, walls, ceilings, tabletops) which are not involved in direct delivery of patient care in healthcare facilities

Hoyer lift - an apparatus which facilitates the repositioning of the non-ambulatory patient from bed to wheelchair or gurney and subsequently to therapy equipment (i.e., immersion tanks).

Hubbard tank - a tank used in hydrotherapy which may accommodate whole-body immersion, such as may be indicated for burn therapy. Use of a Hubbard tank has largely been replaced by bedside post-lavage therapy for wound care management.

HVAC - Heating, Ventilation, Air Conditioning.

Iatrogenic - induced in a patient by a physician’s activity, manner, or therapy. Used especially in reference to an infectious disease or other complication of medical treatment.

Impactor - an air sampling device in which particles and microorganisms are directed onto a solid surface and retained there for assay.

Impingement - an air sampling method during which particles and microorganisms are directed into a liquid and retained there for assay.

Indirect transmission - involves contact of a susceptible host with a contaminated intermediate object, usually inanimate.

Induction unit - the terminal unit of an in-room ventilation system. Induction units take centrally conditioned air and further moderate its temperature. Induction units are not appropriate for areas with high exhaust requirements (e.g., research laboratories).

Intermediate-level disinfection - a disinfection process which inactivates vegetative bacteria, most fungi, mycobacteria, and most viruses (particularly the enveloped viruses), but does not inactivate bacterial spores.

Isoform - a possible configuration of a protein molecule, with a particular tertiary structure. With CJD prion proteins, for example, the molecules with large amounts of "-conformation are the normal isoform or version of that particular protein, whereas those prions with large amounts of $-sheet conformation are the proteins associated with the development of spongiform encephalopathy.

Laminar flow - HEPA filtered air that is blown into a room at a rate of 90 ± 10 feet/min in a unidirectional pattern with 100 - 400 ACH.

Large enveloped virus - viruses whose particle diameter is greater than 50 nm and whose outer surface is covered by a lipid-containing structure derived from the membranes of the host cells. Examples of large enveloped viruses include influenza viruses, herpes simplex viruses, poxviruses.

Laser plume - the transfer of electromagnetic energy into tissues which results in a release of particles, gases, and tissue debris.

Lipid-containing viruses - viruses whose particle contains lipid components. The term is roughly synonymous with enveloped viruses whose outer surface is derived from host cell membranes. Lipid-containing viruses are sensitive to the inactivating effects of liquid chemical germicides.

Lithotriptors - instruments used for crushing caliculi (i.e., stones, sand) in the bladder or kidneys.

Low efficiency filter - the prefilter with a particle-removal efficiency of approximately 30% through which incoming air first passes. See also Prefilter.

Low-level disinfection - a disinfection process which will inactivate most vegetative bacteria, some fungi, and some viruses, but cannot be relied on to inactivate resistant microorganisms (e.g., mycobacteria or bacterial spores).

Makeup air - outdoor air supplied to replace exhaust air and filtration.

Makeup water - cold water supply source for a cooling tower..173

Manometer - a device which measures the pressure of liquids and gases. A manometer is commonly used to verify air filter performance by measuring pressure differentials on either side of the filter.

Membrane filtration - an assay method suitable for recovery and enumeration of microorganisms from liquid samples.

Mesophilic - that which favors a moderate temperature. For mesophilic bacteria, a temperature range of 20°C - 55°C (68°F - 131°F) is favorable for their growth and proliferation.

Mixing box - site where the cold and hot air streams mix in the HVAC system, usually situated close to the air outlet for the room.

Mixing faucet - a faucet which mixes hot and cold water to produce water at a desired temperature.

MMAD - Mass Median Aerodynamic Diameter: the unit used by ACGIH to describe the size of particles when particulate air sampling is conducted.

Moniliaceous - hyaline or brightly colored; laboratory terminology for the distinctive characteristics of certain opportunistic fungi in culture (e.g., Aspergillus spp., Fusarium spp.).

Monochloramine - the result of the reaction between chlorine and ammonia that contains only one chlorine atom.

Natural ventilation - the movement of outdoor air into a space through intentionally provided openings (i.e., windows, doors, nonpowered ventilators).

Negative pressure - air pressure differential between two adjacent airspaces such that airflow is directed into the room relative to the corridor ventilation (i.e., room air is prevented from flowing out of the room and into adjacent areas).

Neutropenia - a medical condition in which the patient’s concentration of neutrophils is substantially less than that in the normal range. Severe neutropenia occurs when the concentration is <1,000 polymorphonuclear cells/µL for 2 weeks or <100 polymorphonuclear cells /mL for 1 week, particularly for hematopoietic stem cell transplant (HSCT) recipients.

Non-critical devices - these medical devices or surfaces come into contact with only intact skin. The risk of infection from using these devices is low.

Non-enveloped virus - a virus whose particle is not covered by a structure derived from a membrane of the host cell. Non-enveloped viruses have little or no lipid compounds in their biochemical composition, which is significant to their inherent resistance to the action of chemical germicides.

Nosocomial - an occurrence, usually an infection, that is acquired in a hospital as a result of medical care.

Nuisance dust - generally innocuous dust, not recognized as the direct cause of serious pathological conditions.

Oocysts - a cyst in which sporozoites are formed; a reproductive aspect of the life cycle of a number of parasitic agents (i.e., Cryptosporidium spp., Cyclospora spp.)

Outdoor air - air taken from the external atmosphere and, therefore, not previously circulated through the system.

Parallel streamlines - a unidirectional airflow pattern achieved in a laminar flow setting, characterized by little or no mixing of air.

Particulate matter (particles) - a state of matter in which solid or liquid substances exist in the form of aggregated molecules or particles. Airborne particulate matter is typically in the size range of 0.01 - 100 µm diameter.

Pasteurization - a disinfecting method for liquids during which the liquids are heated to 60°C (140°F) for a short time (>30 mins.) to significantly reduce the numbers of pathogenic or spoilage microorganisms.

Plinth - a treatment table, a piece of equipment used to reposition the patient for treatment.

Portable room-air HEPA recirculation units - free-standing portable devices that remove airborne contaminants by recirculating air through a HEPA filter.

Positive pressure - air pressure differential between two adjacent air spaces such that airflow is directed from the room relative to the corridor ventilation (i.e., air from corridors, adjacent areas is prevented from entering the room).

Potable (drinking) water - water that is fit to drink. The microbiological quality of this water as defined by EPA microbiological standards from the Surface Water Treatment Rule: 1) Giardia lamblia: 99.9% killed/inactivated; 2) viruses: 99.9% inactivated; 3) Legionella spp.: no limit, but if Giardia and viruses are inactivated, Legionella will also be controlled; 4) heterotrophic plate count [HPC]: < 500 CFU/mL; and 5) > 5% of water samples total coliform-positive in a month.

PPE - Personal Protective Equipment

ppm - parts per million. A measure of concentration in solution. A 5.25% chlorine bleach solution (undiluted as supplied by the manufacturer) contains approximately 50,000 parts per million of free available chlorine.

Prefilter - the first filter for incoming fresh air in a HVAC system that is approximately 30% efficient in removing particles from the air. See also low-efficiency filter.

Prion - a class of agents associated with the transmission of diseases knowns as transmissible spongiform encephalopathies (TSEs). Prions are considered to consist of protein only, and the abnormal isoform of this protein is thought to be the agent which causes diseases such as Creutzfeldt-Jakob disease (CJD), kuru, scrapie, bovine spongiform encephalopathy (BSE), and the human version of BSE which is variant CJD (vCJD).

Pseudoepidemic (pseudo-outbreak) - a cluster of positive microbiologic cultures in the absence of clinical disease that results from contamination of the laboratory apparatus and process used to recover microorganisms.

Pyrogenic - an endotoxin burden such that a patient would receive > 5 endotoxin units (EU) per kilogram of body weight per hour, thereby causing a febrile response. In dialysis this usually refers to water or dialysate having endotoxin concentrations of > 5 EU/mL.

Rank order - a strategy for assessing overall indoor air quality and filter performance by comparing airborne particle counts from highest to lowest (i.e., from the best filtered air spaces to those with the least filtration).

RAPD - genotyping microorganisms by randomly amplified polymorphic DNA, a method of polymerase chain reaction. Recirculated air - air removed from the conditioned space and intended for reuse as supply air.

Relative humidity - the ratio of the amount of water vapor in the atmosphere to the amount necessary for saturation at the same temperature. Relative humidity is expressed in terms of percent and measures the percentage of saturation. At 100% relative humidity, the air is saturated. The relative humidity decreases when the temperature is increased without changing the amount of moisture in the air.

Reprocessing (of medical instruments) - the procedures or steps taken to make a medical instrument safe for use on the next patient. Reprocessing encompasses both cleaning and the final or terminal step (i.e., sterilization or disinfection) which is determined by the intended use of the instrument according to the Spaulding classification.

Residuals - the presence and concentration of a chemical in media (e.g., water) or on a surface after the chemical has been added.

Reservoir - a nonclinical source of infection.

Respirable particles - those particles that penetrate into and are deposited in the nonciliated portion of the lung. Particles > 10 µm in diameter are not respirable.

Return air - air removed from a space to be then recirculated or exhausted.

Reverse-osmosis (RO) - an advanced method of water or wastewater treatment that relies on a semi-permeable membrane to separate waters from pollutants. An external force is used to reverse the normal osmotic process resulting in the solvent moving from a solution of higher concentration to one of lower concentration.

Riser - water piping which connects the circulating water supply line, from the level of the base of the tower or supply header, to the tower’s distribution system.

RODAC - Replicate Organism Direct Agar Contact. A nutrient agar plate whose convex agar surface is directly pressed onto an environmental surface for the purpose of microbiologic sampling of that surface.

Room-air HEPA recirculation systems and units - devices (either fixed or portable) that remove airborne contaminats by recirculating air through a HEPA filter.

Routine sampling - environmental sampling conducted without a specific, intended purpose and with no action plan dependent on the results obtained.

Sanitizer - an agent that reduces microbial contamination to safe levels as judged by public health standards or requirements.

Saprophytic - a naturally-occurring microbial contaminant.

Sedimentation - the act or process of depositing sediment from suspension in water, letting solids settle out of wastewater by gravity during treatment.

Semi-critical devices - medical devices that come into contact with mucous membranes or non-intact skin.

Service animal - any animal individually trained to do work or perform tasks for the benefit of a person with a disability.

Shedding - generation of particles and spores by sources within the patient area, such as patient movement and airflow over surfaces.

Single-pass ventilation - ventilation in which 100% of the air supplied to an area is exhausted to the outside.

Small, non-enveloped viruses - viruses whose particle diameter is less than 50 nm and whose outer surface is the protein of the particle itself and not that of host cell membrane components. Examples of small, non-enveloped viruses are polioviruses, hepatitis A virus.

Spaulding Classification - the categorization of inanimate surfaces in the medical environment as proposed in 1972 by Dr. Earle Spaulding. Surfaces are divided into three general categories, based on the theoretical risk of infection if the surfaces are contaminated at time of use. The categories are "critical," "semi-critical," and "non-critical."

Specific humidity - the mass of water vapor per unit mass of moist air. It is usually expressed as grains of water per pound of dry air, or pounds of water per pound of dry air. The specific humidity changes as moisture is added or removed. However, temperature changes do not change the specific humidity unless the air is cooled below the dew point.

Splatter - visible drops of liquid or body fluid which are expelled forcibly into the air and settle out quickly, as distinguished from particles of an aerosol which remain airborne indefinitely.

Steady state - the usual state of an area.

Sterilization - the use of a physical or chemical procedure to destroy all microbial life, including large numbers of highly resistant bacterial endospores.

Stop valve - a valve that regulates the flow of fluid through a pipe; a faucet.

Substitution fluid - fluid which is used for fluid management of patients receiving hemodiafiltration. This fluid can be prepared on-line at the machine through a series of ultrafilters or with the use of sterile peritoneal dialysis fluid.

Supply air - that air delivered to the conditioned space and used for ventilation, heating, cooling, humidification, or dehumidification.

Tensile strength - the resistance of a material to a force tending to tear it apart, measured as the maximum tension the material can withstand without tearing.

Therapy animal - an animal, usually a personal pet that, with their owners, provide supervised, goal-directed intervention to clients in hospitals, nursing homes, special-population schools, and other treatment sites.

Thermophilic - capable of growing in environments warmer than body temperature.

Thermotolerant - capable of withstanding high temperature conditions.

TLV® - An exposure level under which most people can work consistently for 8 hours a day, day after day, without adverse effects. Used by the ACGIH to designate degree of exposure to contaminants. TLV® can be expressed as approximate milligrams of particulate per cubic meter of air (mg/m 3 ). TLVs® are listed as either an 8-hour TWA (time weighted average) or a 15-minute STEL (short term exposure limit).

TLV-TWA - Threshold Limit Value-Time Weighted Average: the time-weighted average concentration for a normal 8- hour workday and a 40-hour workweek to which nearly all workers may be exposed repeatedly, day after day, without adverse effects. The TLV-TWA for "particulates (insoluble) not otherwise classified" (PNOC) - (sometimes referred to as nuisance dust) - are those particulates containing no asbestos and <1% crystalline silica. A TLV-TWA of 10 mg/m3 for inhalable particulates and a TLV-TWA of 3 mg/m3 for respirable particulates (particulates <5 µm in aerodynamic diameter) have been established.

Total suspended particulate matter - the mass of particles suspended in a unit of volume of air when collected by a high-volume air sampler.

Transient - a change in the condition of the steady state that takes a very short time compared with the steady state. Opening a door, and shaking bed linens are examples of transients.

TWA - Average exposure for an individual over a given working period, as determined by sampling at given times during the period. TWA is usually presented as the average concentration over an 8-hour workday for a 40-hour workweek.

Ultraclean air - air in laminar flow ventilation which has also passed through a bank of HEPA filters.

Ultrafiltered dialysate - the process by which dialysate is passed through a filter having a molecular weight cut-off of approximately 1 kilodalton for the purpose of removing bacteria and endotoxin from the bath.

Ultraviolet germicidal irradiation (UVGI) - the use of ultraviolet radiation to kill or inactivate microorganisms.

Ultraviolet germicidal irradiation lamps - lamps that kill or inactivate microorganisms by emitting ultraviolet germicidal radiation, predominantly at a wavelength of 254 nm. UVGI lamps can be used in ceiling or wall fixtures or within air ducts of ventilation systems.

Vapor pressure - the pressure exerted by free molecules at the surface of a solid or liquid. Vapor pressure is a function of temperature - it increases as the temperature increases.

Vegetative bacteria - bacteria which are actively growing and metabolizing, as opposed to a bacterial state of quiescence which is achieved when certain bacteria (i.e., gram-positive bacilli) convert to spores when the environment can no longer support active growth.

Vehicle - any object, person, surface, fomite, or media which may carry and transfer infectious microorganisms from one site to another.

Ventilation - the process of supplying and removing air by natural or mechanical means to and from any space. Such air may or may not be conditioned.

Ventilation air - that portion of the supply air that is outdoor air plus any recirculated air that has been treated for the purpose of maintaining acceptable indoor air quality.

Ventilation, dilution - an engineering control technique to dilute and remove airborne contaminants by the flow of air into and out of an area. Air that contains droplet nuclei is removed and replaced by contaminant-free air. If the flow is sufficient, droplet nuclei become dispersed, and their concentration in the air is diminished.

Ventilation, local exhaust - ventilation used to capture and removed airborne contaminants by enclosing the contaminant source (i.e., the patient) or by placing an exhaust hood close to the contaminant source.

v/v - volume to volume. An expression of concentration of a percentage solution when the principle component is added as a liquid to the diluent.

w/v - weight to volume. An expression of concentration of a percentage solution when the principle component is added as a solid to the diluent.

Weight-arrestance - a measure of filter efficiency, used primarily when describing the performance of low- and medium-efficiency filters. A standardized synthetic dust is fed to the filter, and the weight fraction of the dust removed is determined.

Microorganisms have a tendency to associate with and stick to surfaces. These adherent organisms can initiate and develop biofilms, which are comprised of cells embedded in a matrix of extracellularly produced polymers and associated abiotic particles.1315 It is inevitable that biofilms will form in most water systems, and in the healthcare facility environment, biofilms may be found in the potable water supply piping, hot water tanks, air conditioning cooling towers, or in sinks, sink traps, aerators, or shower heads. Biofilms, especially in water systems, are not present as a continuous slime or film, but are more often scanty and heterogeneous in nature.1316 Biofilms may form under stagnant as well as flowing conditions, so storage tanks, in addition to water system piping, may be vulnerable to the development of biofilm, especially if water temperatures are low enough to allow the growth of thermophilic bacteria such as Legionella spp. And if these structures and equipment are not cleaned for extended periods of time.1317

Algae, protozoa, and fungi may be present in biofilms, but the predominant microorganisms of water system biofilms are gram negative bacteria. Although most of these organisms will not normally pose a problem for healthy individuals, certain biofilm bacteria (e.g., Pseudomonas aeruginosa, Klebsiella spp., Pantoea agglomerans, Enterobacter cloacae) all may be agents for opportunistic infections for immunocompromised individuals.1318, 1319 These biofilm organisms may easily contaminate indwelling medical devices or intravenous (IV) fluids, and could be transferred on the hands of health care workers.1318 - 1321 Biofilms may potentially provide an environment for the survival of pathogenic organisms, such as Legionella pneumophila and E. coli O157:H7. Although the association of biofilms and medical devices provides a plausible explanation for a variety of healthcare-associated infections, it is not clear how the presence of biofilms in the water system may influence the rates of healthcare-associated waterborne infection. Organisms within biofilms behave quite differently than their planktonic (free floating) counterparts.

Research has shown that biofilm-associated organisms are more resistant to antibiotics and disinfectants than are planktonic organisms, either because the cells are protected by the polymer matrix, or because they are physiologically different.1322 - 1327 Nevertheless, municipal water utilities attempt to maintain a chlorine residual in the distribution system to discourage microbiological growth. Though chlorine in its various forms is a proven disinfectant, it has been shown to be less effective against biofilm bacteria.1325 Higher levels of chlorine for longer contact times are necessary to eliminate biofilms.

Routine sampling of healthcare facility water systems for biofilms is not warranted. If an epidemiologic investigation points to the water supply system as a possible source of infection, then water sampling for biofilm organisms should be considered so that prevention and control strategies can be developed. Once a biofilm is established, it is difficult to totally remove in existing piping. Strategies to remediate biofilms in a water system would include flushing the system piping, hot water tank, dead legs, and those areas of the facility’s water system subject to low or intermittent flow. The benefits of this treatment would include: 1) elimination of corrosion deposits and sludge from the bottom of hot water tanks; 2) removal of biofilms from shower heads and sink aerators; and 3) circulation of fresh water containing elevated chlorine residuals into the healthcare facility water system.

The general strategy for evaluating water system biofilm depends on a comparision of the bacteriological quality of the incoming municipal water and that of water sampled from within facility’s distribution system.

Heterotrophic plate counts and coliform counts, both of which are routinely run by the municipal water utility, will at least provide in indication of the potential for biofilm formation. Heterotrophic plate count levels in potable water should be <500 CFU/mL. These levels may increase on occasion, but counts consistently >500 CFU/mL would indicate a general decrease in water quality. A direct correlation between heterotrophic plate count and biofilm levels has been demonstrated.1327 Therefore, an increase in heterotrophic plate count would suggest a greater rate and extent of biofilm formation in a healthcare facility water system. The water supplied to the facility should also contain <1 coliform bacteria/100 mL. Coliform bacteria are indicator organisms whose presence in the distribution system could indicate the presence of fecal contamination. It has been shown that coliform bacteria can colonize biofilms within drinking water systems, hence intermittant contamination of a water system with these organisms could lead to colonization of the system.

Water samples can be collected from throughout the healthcare facility system, including both hot and cold water sources; samples should be cultured by standard methods.895 If heterotrophic plate counts in the facility water system are higher than those at the point of water entry to the building, it can be concluded that the facility water quality has diminished. If biofilms are detected in the facility water system and determined by an epidemiologic and environmental investigation to be a reservoir for healthcare-associated pathogens, the municipal water supplier could be contacted with a request to provide higher chlorine residuals in the distribution system, or the healthcare facility could consider installing a supplemental chlorination system.

Sample collection sites for biofilm in healthcare facilities include hot water tanks, and shower heads and faucet aerators, especially in immunocompromised patient-care areas. Swabs should be placed into tubes containing phosphate buffered water, pH 7.2 or phosphate buffered saline, shipped to the laboratory under refrigeration and processed within 24 hrs. of collection by vortexing with glass beads and plated onto a nonselective medium (e.g., Plate Count Agar or R2A medium) and selective media (e.g., media for Legionella spp. isolation) after serial dilution. If the plate counts are elevated above levels in the water (i.e. comparing the plate count per square centimeter of swabbed surface to the plate count per milliter of water), then biofilm formation can be suspected. In the case of an outbreak, it would be advisable to isolate organisms from these plates to determine whether the suspect organisms are present in the biofilm or water samples and compare them to the organisms isolated from patient specimens.

In order to detect the low total viable heterotrophic plate counts outlined by the current AAMI standards for water and dialysate in dialysis settings, it is necessary to use standard quantitative culture techniques with appropriate sensitivity levels.792, 793 The membrane filter technique is particularly suited for this application because it permits large volumes of water to be assayed.794 Since the membrane filter technique may not be readily available in clinical laboratories, the spread plate assay can be used as an alternative.794 If the spread plate assay is used, however, the standard prohibits the use of a calibrated loop when applying sample to the plate. The prohibition is based on the low sensitivity of the calibrated loop. A standard calibrated loop transfers 0.001 mL of sample to the culture medium, so that the minimum sensitivity of the assay is 1,000 CFU/mL. This level of sensitivity is unacceptable when the maximum allowable limit for microorganisms is 200 CFU/mL. Therefore, when the spread plate method is used, a pipette must be used to place 0.1 to 0.5 mL of water on the culture medium.

The current AAMI Standard specifically prohibits the use of nutrient-rich media (e.g., blood agar, chocolate agar) in dialysis water and dialysate assays because these culture media are too rich for growth of the naturally occurring organisms found in water. Debate continues within AAMI, however, as to the most appropriate culture medium and incubation conditions to be used. The original clinical observations on which the microbiological requirements of this standard were based used Standard Methods Agar (SMA), a medium containing relatively few nutrients.642 The use of Tryptic Soy Agar (TSA), a general purpose medium for isolating and cultivating microorganisms was recommended in later versions of the standard because it was thought more appropriate for culturing bicarbonate-containing dialysate.749, 750, 795 Moreover, culturing systems based on TSA are readily available from commercial sources. Several studies, however, have shown that the use of nutrient-poor media, such as R2A, results in an increased recovery of bacteria from water.1328, 1329 The original standard also specified incubation for 48 hours at 35°C - 37°C (95°F -98.6° F) before enumeration of bacterial colonies. Extending the culturing time up to 168 hours, or 7 days and using incubation temperatures of 23°C - 28°C (73.4°F - 82.4°F) have also been shown to increase the recovery of bacteria.1328, 1329 Other investigators, however, have not found such clear cut differences between culturing techniques.795, 1330 After considerable discussion, the AAMI Committee has not reached a consensus regarding changes in the assay technique, and the use of TSA for 48 hours at 37/C (98.6°F) remains the recommended method. It should be recognized, however, that these culturing conditions may underestimate the bacterial burden in the water and fail to identify the presence of some organisms.

Specifically, the recommended method may not detect the presence of various NTM that have been associated with several outbreaks of infection in dialysis units.31, 32 In these instances, however, the high numbers of mycobacteria in the water were related to the total heterotrophic plate counts, each of which was significantly greater than that allowable by the AAMI Standard.

Endotoxin can be tested by one of two types of assays - kinetic (colorimetric or turbidimetric) or gel-clot. Endotoxin units are assayed by the Limulus Amebocyte Lysate (LAL) method. Because endotoxins differ in their activity on a mass basis, their activity is referred to a standard Escherichia coli endotoxin. The current standard (EC-6) is prepared from E. coli O113:H10. The relationship between mass of endotoxin and its activity varies with both the lot of LAL and the lot of control standard endotoxin used. Since standards for endotoxin were harmonized in 1983 with the introduction of EC-5, the relationship between mass and activity of endotoxin has been approximately 5 - 10 EU/ng. Studies to harmonize standards have led to the measurement of endotoxin units (EU) where 5 EU is equivalent to 1 ng E. coli O55:B5 endotoxin.1331

In summary, water used to prepare dialysate and to reprocess hemodialyzers should not contain a total microbial count >200 CFU/mL as determined by assay on TSA agar for 48 hrs. at 36°C (96.8°F), and no more than 5 endotoxin units (EU) per mL. Currently the EU standard applies only to the water used to reprocess the hemodialyzers. The dialysate at the end of a dialysis treatment should not contain >2,000 CFU/mL.31, 32, 644, 750

Legionella spp. are ubiquitous and can be isolated from 20% - 40% of freshwater environments, including man-made water systems.1332, 1333 In healthcare facilities, however, it is difficult to determine a course of remedial action based on the presence of legionellae in potable water since it appears that their presence rarely results in disease among immunocompetent patients.

The issue of regularly scheduled microbiological monitoring for legionellae remains controversial, as detection of legionellae in an environmental source is not necessarily evidence of the potential for disease.1334

There is general agreement that monitoring is warranted in order to identify the source of an outbreak of legionellosis or to evaluate the efficacy of biocides or prevention measures. CDC recommends aggressive maintenance/disinfection protocols for devices known to transmit legionellae but does not recommend regularly scheduled microbiologic assays for the bacteria.405 Monitoring the water, however, may be considered in special settings where people are highly susceptible to illness and mortality due to Legionella infection (e.g., HSCT units, organ transplant units) within a hospital.9 In the absence of associated disease, however, there is no clear evidence that basing interventions on microbiologic assays will lead to a reduction in Legionnaires' disease cases or outbreaks.

Examination of water samples is the most efficient microbiologic method for identifying sources of legionellae, which is an integral part of an epidemiologic investigation into healthcare-associated

Legionnaires’ disease. Because of the diversity of plumbing and HVAC systems in healthcare facilities, the number and types of sites that should be tested must be determined on an individual basis prior to collection of water samples. A previously published environmental sampling protocol that addressed sampling site selection in hospitals can serve as a prototype for sampling in other institutions.1122 Any water source that may be aerosolized should be considered a potential source for the transmission of legionellae. The bacteria are rarely found in municipal water supplies and tend to colonize plumbing systems and point-of-use devices. To colonize a system the bacteria must multiply and this requires temperatures >25°C (>77°F).1335

Therefore, legionellae are most commonly found in hot water systems. The bacteria do not survive drying, so condensate from air-conditioning equipment, which frequently evaporates, is not a likely source.1336

Water samples and swabs of point-of-use devices or system surfaces should be collected when sampling for legionellae.1314 Swabs of system surfaces (Table C.1) allow sampling of biofilms, which frequently contain legionellae. When culturing faucet aerators and shower heads, swabs of these surfaces should be collected first; water samples are then collected from these fixtures after the aerators or shower heads are removed.

Collection and culture techniques are outlined in Table C.2. Swabs can be streaked directly onto agar plates if those are readily available at the collection site. If the swabs and water samples must be transported back to a laboratory for processing, immersing the individual swabs in sample water minimizes drying during transit. Place swabs and water samples in insulated coolers to protect the specimens from temperature extremes.

I. Before chemical disinfection and mechanical cleaning:

A. Provide protective equipment to workers who perform the disinfection, to prevent their exposure to a) chemicals used for disinfection and b) aerosolized water containing Legionella sp. Protective equipment may include full-length protective clothing, boots, gloves, goggles, and a full- or half-face mask that combines a HEPA filter and chemical cartridges to protect against airborne chlorine levels of up to 10 mg/L.

B. Shut off cooling-tower.

1. If possible, shut off the heat source.

2. Shut off fans, if present, on the cooling tower/evaporative condenser (CT/EC).

3. Shut off the system blowdown (i.e., purge) valve. Shut off the automated blowdown controller, if present, and set the system controller to manual.

4. Keep make-up water valves open.

5. Close building air-intake vents within at least 30 m of the CT/EC until after the cleaning procedure is complete.

6. Continue operating pumps for water circulation through the CT/EC.

II. Chemical disinfection

A. Add fast-release, chlorine-containing disinfectant in pellet, granular, or liquid form, and follow safety instructions on the product label. Examples of disinfectants include sodium hypochlorite (NaOCl) or calcium hypochlorite (Ca[OCI]2), calculated to achieve initial free residual chlorine (FRC) of 50 mg/L: either 3.0 lbs (1.4 kg) industrial grade NaOCl (12% - 15% available Cl) per 1,000 gal of CT/EC water; 10.5 lbs (4.8 kg) domestic grade NaOCl (3% - 5% available Cl) per 1,000 gal of CT/EC water; or 0.6 lb (0.3 kg) Ca[OCl]2 per 1,000 gal of CT/EC water. If significant biodeposits are present, additional chlorine may be required. If the volume of water in CT/EC is unknown, it can be estimated (in gallons) by multiplying either the recirculation rate in gallons per minute by 10 or the refrigeration capacity in tons by 30. Other appropriate compounds may be suggested by a water-treatment specialist.

B. Record the type and quality of all chemicals used for disinfection, the exact time the chemicals were added to the system, and the time and results of FRC and pH measurements.

C. Add dispersant simultaneously with or within 15 minutes of adding disinfectant. The dispersant is best added by first dissolving it in water and adding the solution to a turbulent zone in the water system. Automatic-dishwasher compounds are examples of low or nonfoaming, silicate-based dispersants. Dispersants are added at 10 - 25 lbs (4.5 -11.25 kg) per 1,000 gal of CT/EC water.

D. After adding disinfectant and dispersant, continue circulating the water through the system. Monitor the FRC by using an FRC-measuring device with the DPD method (e.g., a swimming-pool test kit), and measure the pH with a pH meter every 15 minutes for 2 hours. Add chlorine as needed to maintain the FRC at >10 mg/L. Because the biocidal effect of chlorine is reduced at a higher pH, adjust the pH to 7.5 - 8.0. The pH may be lowered by using any acid (e.g., muriatic acid or sulfuric acid used for maintenance of swimming pools) that is compatible with the treatment chemicals.

E. Two hours after adding disinfectant and dispersant or after the FRC level is stable at >10 mg/L, monitor at 2-hour intervals and maintain the FRC at >10 mg/L for 24 hours.

F. After the FRC level has been maintained at >10 mg/L for 24 hours, drain the system. CT/EC water may be drained safely into the sanitary sewer. Municipal water and sewerage authorities should be contacted regarding local regulations. If a sanitary sewer is not available, consult local or state authorities (e.g., Department of Natural Resources) regarding disposal of water. If necessary, the drain-off may be dechlorinated by dissipation or chemical neutralization with sodium bisulfite.

G. Refill the system with water and repeat the procedure outlined in steps 2-6 in Section I-B above.

III. Mechanical cleaning

A. After water from the second chemical disinfection has been drained, shut down the CT/EC.

B. Inspect all water-contact areas for sediment, sludge, and scale. Using brushes and/or a low- pressure water hose, thoroughly clean all CT/EC water-contact areas, including the basin, sump, fill, spray nozzles, and fittings. Replace components as needed.

C. If possible, clean CT/EC water-contact areas within the chillers.

IV. After mechanical cleaning

A. Fill the system with water and add chlorine to achieve FRC level of 10 mg/L.

B. Circulate the water for 1 hour, then open the blowdown valve and flush the entire system until the water is free of turbidity.

C. Drain the system.

D. Open any air-intake vents that were closed before cleaning.

E. Fill the system with water. CT/EC may be put back into service using an effective water-treatment program.

1. Provide water at >50°C (122°F) at all points in the heated water system, including the taps. This requires that water in calorifiers (water heaters) be maintained at >60°C (140°F). In the United Kingdom, where maintenance of water temperatures at >50°C (122°F) in hospitals has been mandated, installation of blending or mixing valves at or near taps to reduce the water temperature to <43°C (<109.4°F) has been recommended in certain settings to reduce the risk for scald injury to patients, visitors, and health care workers.692

   However, Legionella spp. can multiply even in short segments of pipe containing water at this temperature. Increasing the flow rate from the hot-water-circulation system may help lessen the likelihood of water stagnation and cooling.679, 1341 Insulation of plumbing to ensure delivery of cold (<20°C [<68°F]) water to water heaters (and to cold-water outlets) may diminish the opportunity for bacterial multiplication.397 Both dead legs and capped spurs within the plumbing system provide areas of stagnation and cooling to <50°C (<122°F) regardless of the circulating water temperature; these segments may need to be removed to prevent colonization.672 Rubber fittings within plumbing systems have been associated with persistent colonization, and replacement of these fittings may be required for Legionella spp. eradication.1342

    

2. Continuous chlorination to maintain concentrations of free residual chlorine at 1-2 mg/L at the tap. This requires the placement of flow-adjusted, continuous injectors of chlorine throughout the water distribution system. The adverse effects of continuous chlorination include accelerated corrosion of plumbing, which results in system leaks and production of potentially carcinogenic trihalomethanes. However, when levels of free residual chlorine are below 3 mg/L, trihalomethane levels are kept below the maximum safety level recommended by the EPA.693, 1343, 1344

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