Infection Control Today: Clinical Update

Waterborne Pathogens:
Whats Lurking in Your Facilitys Pipes?

By Jennifer Schraag

The Centers for Disease Control (CDC) reports that nearly 2 million patients contract infections during their stays in U.S. hospitals. Healthcare-acquired infections (HAIs) in the U.S. resulted in 88,000 deaths in 1995 and their annual cost is estimated to be as much as $5.7 billion, with per patient costs of up to $50,000 per episode.

The numbers involving infection through waterborne pathogens aren't any more heartwarming. The CDC notes that 23 percent of all cases of Legionnaires disease reported in the U.S. during the 1980s was acquired in hospitals, and of these cases, 40 percent died.

"The most common misconception in healthcare settings, and one that education will eradicate, is that waterborne pathogens are not major contributors to HAIs," says Joseph S. Cervia. MD, professor of clinical medicine and pediatrics at the Albert Einstein College of Medicine in New York, and medical director and senior vice president for Pall Medical of Pall Corporation.

A review of waterborne-associated nosocomial infections found an estimated 1,400 deaths occur each year in the U.S. as a result of waterborne nosocomial pneumonias caused by Pseudomonas aeruginosa alone.1 Medical conditions associated with these agents range from colonization of the respiratory and urinary tracts to deep, disseminated infections that can result in pneumonia and bloodstream bacteremia.2 With numbers such as these, it is no doubt that members of the infection control and physical plant departments are pulling out all the stops to contain this never-ending prevalence of waterborne pathogens in healthcare facility water supplies.

Prevelant Waterborne Pathogens

A wide variety of bacteria and fungi are prevalent in water. Cervia says the common waterborne pathogens of primary clinical significance include the bacterias Legionella pneumophila, P. aeruginosa, Stenotrophomonas spp., Mycobacterium spp., Acinetobacter spp., Burkholderia spp., Enterbacter spp., Klebsiella spp., Serratia spp., Nocardia spp., Flavobacterium spp., and Aeromaonas spp.

Fungi, such as Aspergillus fumigatus (nosocomial aspergillosis, thought to be primarily airborne, can be airborne from a water source in the hospital.3), Fusarium solani and Exophiala jeanselmei, are also prevalent.

Finally, protozoa such as Crytosporidium parvum, Giardia lamblia and Acanthamoeba spp. also are found in water.

"Amoebae are of particular interest because they are known to harbor amoeba-resistant bacteria such as L. pneumophila, P. aeruinosa, B. cepacia, B. pseudomallei, M. avium, M. fortuitum, M. simiae and Flavobacterium spp.," Cervia says. "Amoebae containing amoeba-resistant bacteria act like a 'Trojan horse' that protects the bacteria from systemic disinfection technologies and transports them within the healthcare facility water system."

French scientists conducted a study isolating amoeba-associated alpha proteobacteria from water samples taken from intensive care unit (ICU) taps and general hospital reservoir tanks at four university hospitals in Marseilles.4 Eighty-five ICU patients with nosocomial pneumonia also were tested. The scientists isolated 64 bacterial strains identified as Afipia species or close relatives within the Rhizobiaceae subgroup of alpha proteobacteria. Eleven patients were found to have elevated antibody titer. No specific antibodies were found among the 100 controls.

Best Practices and Techniques

Transmission occurs via contact, ingestion, aspiration, or aerosolization of potable water, or via the hands of healthcare workers (HCWs).5 Tap water used for drinking, showering, bathing, ice preparation and rinsing medical devices presents a potential hazard -- especially to at-risk patients.

"It does depend on the chain of infection," says Stacy LC Coffman, BS, MBA, CIC, M(ASCP)SM, RM(NRM), an infection control professional at the University of Iowa Hospitals and Clinics. "You need to have a regular reservoir and a susceptible host and some way for that susceptible host to be in the way of vector (water is the vector) to get the bacteria to the patient."

Dozens of reservoirs lurk in hospitals including hydrotherapy pools and spas, eyewash stations and even flower vases. Waterbath-based blood/fluid warmers using water that does not have an added disinfectant to prevent bacterial growth is another hazard.

Other modes of transmission for waterborne infections may include direct contact, ingestion of water, indirect-contact transmission (e.g., from an improperly reprocessed medical device), inhalation of aerosols dispersed from water sources; and aspiration of contaminated water.6 The first three modes of transmission are commonly associated with infections caused by gram-negative bacteria and nontuberculous mycobacteria (NTM). Aerosols generated from water sources contaminated with Legionella spp. often serve as the vehicle for introducing legionella to the respiratory tract.

In several hospital outbreaks, patients have been infected through exposure to contaminated aerosols generated by cooling towers, showers, faucets, respiratory therapy equipment and room-air humidifiers.7 The pathogens tend to colonize plumbing systems and point-of-use devices, and are most commonly located in hot water systems.8

"They love warm temperature (not too hot, not too cold) and prefer stagnant water in which they can multiply," says Elias Anaissie, MD, professor of medicine and director of the Division of Supportive Care at the Myeloma Institute for Research and Therapy at the University of Arkansas for Medical Sciences.

Matthew J. Arduino, MS, DrPH, lead microbiologist with the Environmental and Applied Microbiology Team at the Epidemiology and Laboratory Branch Division of Healthcare Quality Promotion with theCDC, agrees and adds, "Stagnant water and areas of the distribution system with low flow rates are opportune areas for biofilms to develop. Most of the waterborne pathogens live in the distribution system as community members of biofilms."

"When you get any kind of lime build-up or tuberculated surfaces on the pipes, that is an area where the biofilm can take hold and harbor these harmful bacteria," Coffman adds.

Is it Seasonal?

The changing of the seasons also brings increased factors to consider. "Water quality and source of water may change throughout the year so it is possible that one would see seasonal variations in the types of opportunistic pathogens," says Arduino. Anaissie agrees, adding, it may be "more likely in hot weather because of the increasing pressures on water sources."

A French study examined the seasonal variation in nosocomial Aeromonas hydrophila infection. The high summer prevalence of A. hydrophila infection coincided with periods when water counts from storage tanks were highest. The scientists concluded monitoring A. hydrophila in hospital water should particularly be done during the summer months.9

"There are a large variety of waterborne bacterial, fungal, and protozoan pathogens, and each responds in its own unique way to the changing of the seasons," explains Cervia. "Seasonal variation of water quality is a widely recognized phenomenon that is characterized by changes in water temperature, sediment level, chemical content and the concentration of available nutrients for waterborne microbes. While waterborne pathogens pose a risk in the healthcare setting throughout the year, seasonal variations in water quality impact conditions for biofilm formation and proliferation."

"The key to successful management of waterborne pathogens is to be alert to the threat that they pose throughout the year and to have the proper controls in place at all times," Cervia says.


"Facilities must proactively and routinely test their water for pathogenic microbes, and they must insure that proper water sampling and culturing techniques are being employed," Cervia advises. "The use of improper growth media and incubation conditions will not permit waterborne microbes to be properly isolated and identified. Many facilities insist that they do not have a problem with their water, when in fact they are not using the correct sampling and culturing techniques."

The CDC recommends aggressive disinfection measures for cleaning and maintaining devices known to transmit legionella, but does not recommend regularly scheduled microbiologic assays for the bacteria. Arduino points out the only routine testing recommended by the CDC deals with water and dialysate for hemodialysis applications.

Scheduled microbiologic monitoring for legionella remains controversial because the presence of legionella is not necessarily evidence of a potential for causing disease.

"It is very difficult to do (water culture) surveillance on a regular basis," Coffman adds. "HICPAC [CDC's Healthcare Infection Control Practices Advisory Committee] does not have any recommendation on frequency of culturing. We're lucky here to have a very large microbiology laboratory with a lot of experience, so all of our tests are done internally with the help of our university hygienic laboratory. So, we do on a routine basis, a culture of the water, but we also have available tests for physicians to utilize. The legionella urinary antigen, or for other organisms such as P. aeruginosa culture, would be the quickest and most readily available way to determine those infections.

"You can test water at any given time and it may have organisms in it. It is never sterile, so it is very important to do a risk assessment of your patient population and be vigilant about their health by doing targeted surveillance. It's really important that the clinicians always keep purview of the patients' health and be looking for these infections as well. It's really a joint effort to be proactive in preventing an outbreak," she says.

To Report, or Not Report

The prevalence of waterborne HAIs is debated and point of origin makes it difficult to decipher.

"The problem, I think, is because all of the waterborne organisms are prevalent in the communities as well as in the hospitals," says Coffman. "It is really a question of determining if the infection came to the patient while they were hospitalized. Some of the confusion about the ability to detect when the patient actually became infected due to incubation of the disease [which is two to 10 days] -- whether they were at home or in another care facility or in an acute care hospital -- is, I think, one of the more difficult reasons why there seems to be a lack of knowledge."

Reporting of such incidences could be one aspect to blame. "A big fear of lawsuits and bad publicity is the biggest obstacle to offering safer hospital water," Anaissie points out.

According to the CDC, 43 outbreaks of waterborne nosocomial infections had been reported in the U.S. in a 2002 study. However, the CDC reports this number is far from accurate "due to both under-diagnosing and under-reporting."

"It's kind of controversial in one sense," says Coffman, "many states do not require reporting of these infections so places do not necessarily report it. For instance, not all states have a requirement that legionella pneumonias be reported. Water quality in general being an environmental issue, I think that's what makes it touchy in many ways. I really don't think it's a reticence to report per se, rather a lack of understanding of the ecology of the organisms."

Effective Measures/Case Studies

Waterborne pathogens are present in hot, cold, circulating and stagnant water and clean-up is challenging, at best. A prominent misconception, according to Cervia, is that systemic disinfection technologies alone can totally eradicate waterborne pathogens.

Coffman agrees, "I think one of the common misconceptions in healthcare settings concerning waterborne pathogens are that it's possible water can even be sterile. It just isn't possible. Water is a very active, living thing. So the best thing we can do as healthcare professionals is to consider the fact that we'll always have these organisms with us."

Approaches of long-term Legionella spp. eradication from the plumbing system are rarely successful,10 and a recent survey found that five out of six hospitals in one geographic region of the U.S. had Legionella bacteria in their water supplies.11 In a 13-year study conducted by one of Coffman's associates at the University of Iowa, a clone that was present in the 1980s persisted in a particular building for the duration of the study. "The point is," Coffman explains, "once it is in your supply, the best you can do is suppress it to its lowest levels. You will probably never get rid of it."
A similar study examined an outbreak of infections caused by L. pneumophila serogroup 5.12 The water distribution system had been sanitized using superheat and flush sanitation, but the epidemic strain was shown to be persisting in the hospital water outlets several years after its initial discovery. Finnish scientists also found the diversity of legionella strains in a hospital water system remains stable over the years, regardless of the use of recommended disinfection procedures.13

"Facility personnel should develop realistic expectations regarding the capabilities of these technologies," Cervia says. "Namely that they cannot totally eradicate resident biofilm in water delivery systems and they cannot respond effectively to sudden microbial challenges derived from seasonal water quality variations, new facility construction and facility renovation activities."

To decrease the prevalence of waterborne pathogens to a controllable level, combinations of several methods are imperative. Such methods may include treating water with chlorine dioxide, heavy metal ions such as copper/silver ions and ultraviolet (UV) light -- all of which have limited the growth of legionella under laboratory and operating conditions.14

"Any facility contemplating disinfection of its water supply system without special equipment (e.g., hot water flush), initial installation of a systemic water disinfection system, or the conversion from one type of system to another, must perform the appropriate research to evaluate the initial purchase and installation costs, running costs to maintain the system and expected efficacy of the technology," Cervia says. "Keeping abreast of the latest literature on these systems is also essential in order to obtain a thorough understanding of their strengths and weaknesses with respect to short-term and long-term efficacy."

After years of clinical studies, sampling and internal testing, Coffman and her coworkers have come up with a full line of defensive mechanisms to fight against waterborne pathogens.

"We have had many controls in place for many years, and a variety of methods have been used here [University of Iowa Hospitals and Clinics]," she says. "We use a combination of copper/silver and chlorine dioxide, we have some filters, we are aware of the technology for UV light disinfection. There are other methods to attempt to clean out the pipes -- should the biofilm get so large that it is well-entrenched -- and to reduce it to levels until it is undetectable; that includes superheating and flushing the water. Also hyperchlorination, if that's possible within the infrastructure."

Another concern for clean-up measures is if the method will be effective for both hot and cold water. A heat-shock unit was used to decrease legionella and NTM in the water systems of a tertiary care hospital where nosocomial infections due to the two genera had been verified.15 Though the unit decreased the levels found in the hot water system, mycobacteria were constantly present in the incoming cold water and were never isolated from the circulating hot water.

"Much attention is focused, and rightfully so, upon L. pneumophila in the recirculating hot water systems of healthcare facilities," Cervia says. "However, many microbial pathogens are also present in cold water, and failure to take the appropriate measures to pay attention to cold water is to ignore a potentially significant problem. Furthermore, an effort must be made to understand the physical layout of the water delivery system and not only correct existing design flaws that lead to water stagnation, but also prevent the formation of new foci that can promote biofilm formation through water stagnation."
Taps, faucets, etc., should be factored into regular maintenance needs, according to Coffman. Others may disagree, citing cost is too exorbitant, however, "whenever you consider what an outbreak may cost, it is often much more cost effective to prevent the infection," she points out.

Cervia agrees and says such measures should be undertaken on an ongoing basis, rather than merely as a reaction to a recognized outbreak. "There is a misconception that point-of-use filtration as an adjunct to systemic disinfection technologies is unnecessary and too expensive to maintain. The value propositions associated with point-of-use filtration, such as cost savings when compared to the use of bottled water and sterile water, fewer HAIs, decreased lengths-of-stay and decreased antimicrobial costs, all must be more effectively communicated."

He adds the use of 0.2 micron filters at the point-of-use (e.g., faucets, showers, ice machines, drinking fountains, hydrotherapy equipment, etc.) to complement systemic disinfection technologies by trapping those waterborne microbes that inevitably survive systemic disinfection, also is imperative.

"The best approach for faucets is to remove aerators completely and replace them with 0.2 micron point-of-use filters," Cervia says. "Similarly, conventional shower heads should also be removed and replaced entirely with point-of-use filters. Finally, in-line filters can be placed slightly upstream of drinking fountains and ice machines to control waterborne pathogens. Thorough draining, cleaning, disinfection and drying of such equipment after each use also are essential in preventing patient-to-patient microbial transmission via these devices. The use of water filtered to trap waterborne pathogens can also effectively decrease the inoculum density to which at-risk patients are exposed."

Preventive Measures

"The issue is not more or less how did it get there, but is it in a situation where it may be causing disease in a patient," Coffman offers.

Measures must be taken to prevent the spread of these organisms. Measures may include hand hygiene, glove use, barrier precautions and eliminating potentially contaminated environmental reservoirs. Water system design may play a big part in stemming outbreaks, and water should not be allowed to stagnate and should be circulated at proper temperatures. Storage tanks and calorifiers should be regularly inspected, cleaned and disinfected as well.

Restricting the use of tap water in high-risk populations interrupts transmission of waterborne pathogens.16 Anaissie also advises strict infection control policies which include no water treatment for high-risk patients during the high-risk periods.

"The expanding base of knowledge concerning the potential pathogenicity of many waterborne microbes, as well as our knowledge of biofilm formation and shedding in complex water delivery systems mandates the restriction of tap water for high-risk patients," Cervia adds.

Coffman says one of her facility's infection control measures is no tap water use on fresh or open wounds. In addition, "when we isolate legionella from our water, we will send out water restrictions to prevent transmission to patients. That includes using bottled water, no showering, brushing teeth only with bottled water, using sterile water regularly in patient care, cleaning of their items and that sort of thing. Making sure humidifiers are using clean water. Restrictions may also include shower restrictions after surgery," she says.

Arduino offers further advice. A few key points include, "clean and disinfect sinks and wash basins on a regular basis; avoid placing decorative fountains and fish tanks in patient-care areas; and maintain constant recirculation in hot water distribution systems serving patient-care areas."

Anaissie adds he'd also like to see the CDC mandate education of HCWs about the risks of tap water for high-risk patients.

Teamwork is Key

"It's really the only way," according to Coffman. IC teams must initiate teamwork throughout the facility and keep it at the forefront of thought in order to win the battle against waterborne pathogens.
Communication between clinicians, IC practitioners and facilities management personnel is critical to the success of any team-oriented program designed to control waterborne pathogens," says Cervia. "Effective communication between clinicians and IC practitioners is essential to identify HAI trends and to locate geographical "hot spots" within the facility. Facilities management personnel must in turn properly maintain the systemic disinfection system. Finally, IC practitioners and facilities management personnel must work in tandem to develop and implement strategy."
Infection control teams also must work closely with hospital engineering and technical services departments -- and hospital management -- as well as ensure physicians and others have a heightened awareness of these types of HAIs.17

"We work very closely with housekeeping and facilities maintenance," Coffman says. "Facilities maintenance, for example, understands the ins and outs of the plumbing system. Knowing the ins and outs of the plumbing system is very important in controlling waterborne organisms, and it's usually those people that have worked on those pipes for years that generally know exactly where the kinks in the pipes are.

"Our facility's housekeeping has been flushing the water in patient rooms while they are in cleaning," Coffman continues. "So, they will enter a patient's room and turn on the water in the sink, and the water in the shower, and let them run for the five or ten minutes it takes them to do the daily cleaning of the patient's room."


1. Anaissie EJ, et. Al. "The hospital water supply as a source of nosocomial infections: a plea for action." Arch Intern Med. 2002 Jul 8;162(13):1483-92.
2. Centers for Disease Control and Prevention. "Guideline for Environmental Infection Control in Health-Care Facilities, 2003." Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC)
3. Anaissie EJ, Costa SF. "Nosocomial aspergillosis is waterborne." Clin Infect Dis. 2001 Nov 1;33(9):1546-8. Epub 2001 Sep 24. Review
4. La Scola B, et. Al. "Patients in the intensive care unit are exposed to amoeba-associated pathogens." Infect Control Hosp Epidemiol. 2002 Aug;23(8):462-5
5. Squier C, et. Al. "Waterborne Nosocomial Infections." Curr Infect Dis Rep. 2000 Dec;2(6):490-496
6. Centers for Disease Control and Prevention. "Guideline for Environmental Infection Control in Health-Care Facilities, 2003." Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee (HICPAC)
7. Centers for Disease Control and Prevention. "Guidelines for Prevention of Nosocomial Pneumonia" MMWR 46(RR-1);1-79, Jan. 1997
8. Centers for Disease Control and Prevention. "Water Sampling Strategies and Culture Techniques for Detecting Legionellae" Recommendations and Reports June 6, 2003/52(RR10);43, Appendix
9. Picard B, Goullet P. "Seasonal prevalence of nosocomial Aeromonas hydrophila infection related to aeromonas in hospital water." J Hosp Infect. 1987 Sep;10(2):152-5
10. Vonberg RP, et. Al. "Reusable terminal tap water filters for nosocomial legionellosis prevention." Ann Hematol. 2005 Jun;84(6):403-5. Epub 2005 Feb 3
11. Pall Corporation. "A Few Statistics about Waterborne Nosocomial Infections"
12. Perola O, et. Al. "Nosocomial Legionella pneumophila serogroup 5 outbreak associated with persistent colonization of a hospital water system." APMIS. 2002 Dec;110(12):863-8
13. Perola O, et. Al. "Persistent Legionella pneumophila colonization of a hospital water supply: efficacy of control methods and a molecular epidemiological analysis." APMIS. 2005 Jan;113(1):45-53
14. Tablan, Ofelia C, et. Al. "Guidelines for Preventing Health-Care--Associated Pneumonia," 2003 Recommendations of CDC and the Healthcare Infection Control Practices Advisory Committee March 26, 2004/53(RR03);1-36.
15. Kusnetsov J, et. Al. "Colonization of hospital water systems by legionellae, mycobacteria and other heterotrophic bacteria potentially hazardous to risk group patients." APMIS. 2003 May;111(5):546-56
16. Squier C, et. Al. "Waterborne Nosocomial Infections." Curr Infect Dis Rep. 2000 Dec;2(6):490-496
17. O'Neill E, Humphreys H. "Surveillance of hospital water and primary prevention of nosocomial legionellosis: what is the evidence?" J Hosp Infect. 2005 Apr;59(4):273-9

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