Judy H. Angelbeck, PhD

I. What is the problem with Legionella in the hospital?

With the cost of hospital acquired infections topping $5 billion dollars according to the Centers for Disease Control (CDC)¹ and the Joint Commission on Accreditation for Hospitals (JACHO) new standards² aimed at decreasing hospital acquired infections, a heightened focus and new priority has been brought to managing patient exposure in the hospital, especially for immune compromised patients to prevent nosocomial infections. In fact, current guidelines from the CDC for the prevention of Health-care associated pneumonia³ suggest that no Legionella should be present in water sources in hospital units housing severely immune compromised patients like allogeneic bone marrow transplant patients.⁴

Several factors must come together that contribute to nosocomial Legionnaires’ disease. These include:

• Since human-to-human transmission does not occur, there must be an environmental reservoir in the hospital such as hospital water via the taps and showers, reservoir tanks.
• There must be a means of transmitting the bacterium – inhalation of aerosols from contaminated water aerosols contaminating surfaces and medical devices as well as aspiration or swallowing of water.
• There must be a susceptible host – immune compromised patients or neutropenic patients.⁵

The water taps and showers throughout critical care units in the hospital serve to potentially broadcast aerosols that can be contaminated with organisms such as Legionella spp, as well as Pseudomonas spp and Aspergillus spp exposing patients, staff equipment and environmental surfaces.³

II. How does Legionella spp colonize a hospital water distribution system?

The hospital hot water distribution system is not only a reservoir for the nosocomial waterborne pathogen Legionella, but is also an environment for amplification of the bacteria.⁵ A number of design factors in the healthcare water distribution systems contribute to the growth and maintenance of waterborne pathogens like Legionella. These include:

• Temperatures in the water distribution system
• Flow
• Systems for buildings with multiple stories
• Complex distribution systems
• Intermittent use⁶

Biofilm build-up in the hospital water distribution system is the primary contributor to poor water quality and the likely way that Legionella spp get established in these systems. Biofilm is a community of microorganisms adhering to the interior of pipe surfaces surrounded by a slime secreted by the bacteria.^5,7

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Biofilm is resistant to heating and chlorination – “armor plated”

Any part of the distribution system exposed to water and bacteria may form a biofilm.

Contributing Factors:

• Aging systems
• Areas of stagnation
• Flexible shower hoses Biofilm may become dislodged and released

Conditions for Release of Biofilm:

• During periods of increasing demand
• During periods of construction

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In addition to biofilms, Legionella species living inside of amoeba in hospital water systems have been shown by LaScola et al to be associated with ventilatory-associated pneumonia. While amoeba typically feed on bacteria, some bacteria such as Legionella spp and Pseudomonas spp resist digestion by amoeba and live inside the amoeba. So the amoeba in the hospital water distribution system becomes a “Trojan horse” delivering the risk of nosocomial exposure and disease while resisting commonly used disinfectants such as chlorine.^3,8,9

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Amoeba in the hospital water distribution system becomes a “Trojan horse”delivering the risk of nosocomial exposure and disease while resisting commonly used disinfectants such as chlorine.⁹

An amoeba engulfing another organism can serve as a “Trojan” horse protecting bacteria like Legionella from disinfectants in water distribution system.^8,9

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III. Legionella is a high profile waterborne pathogen and ubiquitous in the global environment.

Legionella first achieved notoriety in 1976, when an outbreak of pneumonia occurred at the American Legion convention in Pennsylvania.10,11 Since that time more than 46 Legionella spp have been identified. However 90 percent of human disease is caused by Legionella pneumophila.¹²

In Europe 4,338 cases occurred resulting in 342 deaths in 33 countries in 2002. This represents a 75 percent increase in cases in the last 10 years due in part to better surveillance and detection. About 77 percent of the cases are caused by Legionella pneumophila. While about 300 of those cases were nosocomial, over 900 cases in Europe were not identified as to whether they were community, travel or nosocomial. Since the correct diagnosis of nosocomial Legionnaires’ disease is easily overlooked in the clinical setting, it is underdiagnosed and underreported in the hospital setting.¹³

In North America, Legionella spp is ubiquitous in freshwater and ground water. In 2003 several east coast states in the U.S. experienced a 200 percent to 300 percent rise in reported cases of Legionnaires’ disease increasing the concern of organizations like JACHO about exposure in hospitals to waterborne pathogens. It should be noted that Legionella bacteria are among the top three causes of sporadic community acquired pneumonias and that the American Society of Microbiology News reported in 1995 that 15-30 percent of patients admitted to intensive care units with pneumonia have Legionellosis.¹²

IV. What is the Incidence of Nosocomial Legionellosis?

Determining the actual incidence of nosocomial Legionellosis is very difficult since many cases go undiagnosed because the disease is difficult to distinguish from other forms of pneumonia. Estimates for the incidence of Legionellosis in the U.S vary widely, as shown in the chart below.

Organization Reporting	Incidence of Legionellosis	Nosocomial Incidence   of Legionellosis	Potential Deaths due to Nosocomial Legionellosis
CDC11,12	8000-18,000	23% (1840-4140)	230-518
OSHA11	>25,000	23% (5750)	719
Others cited By AWT*11	100,000	23% (23,000)	2875

* Association of Water Technologies

Note: This table is derived from information on the CDC web site on Legionellosis including the 23 percent incidence of nosocomial cases in the U.S. and from a position statement by the Associations for Water Technologies.

V. Patients in hospital critical care areas are at high-risk for exposure to Legionella.

Hospital critical care areas are a special high risk environment for the occurrence of Legionnaires’ Disease because of the concentration of immune compromised patients including allogeneic and autologous bone marrow transplant patients, solid organ transplant patients, HIV positive patients and other neutropenic patients. These patients are generally housed in special protected environments in the hospital where enhanced or more extraordinary infection control procedures to manage patient exposure to nosocomial pathogens are employed.^3,4,5 These immune compromised patients are at special high risk of nosocomial disease from exposure to waterborne pathogens like Legionella.^3,4,5,14

The table below demonstrates the frequency of contamination of hospital water systems with Legionella spp.

Hospital Surveys for Legionella Contamination of the water Distribution System¹⁵*

Reference	Location	Number of Hospitals	% With Legionella	Isolate
HMSO	United Kingdom	40	70%	L pneumophila Serogroup1
Alary	Quebec	84	68%	L pneumophila Serogroup1-8
Vickers	Western Pennsylvania	15	60%	L pneumophilia Serogroup1-6
Patterson	United Kingdom	69	55%	L pneumophila Legionella species
Marrie	Nova Scotia	39	23%	L pneumophila Legionella longbeachae
Liu	United Kingdom	17	12%	L pneumophilia Serogroups1,4,6
Kool et al17	Texas	15	100%	L pneumophilia

*Note: Source of table Yu VL, /resolving the Controversy on Environmental Cultures for Legionella: A Modest Proposal, Infection Control and Hospital Epidemiology, 1998;19:893-897.

Source of last table entry was Kool et al 17 CDC who found 100 percent of hospitals studied in San Antonio, Texas had water distribution systems colonized by Legionella.

Hospital acquired Legionellosis represents 23 percent of all cases reported in the U.S. according to the CDC^11,17 In addition, the mortality for nosocomial Legionellosis can be very high raging from 9 percent to 100 percent in some reports.¹⁷ The table below identifies nosocomial outbreaks of Legionellosis, the suggested environmental water source of patient exposure and the region where the hospital was located.

Types of patients Infected	Suggested water Source of exposure	Geographic Region
BMT & Heart transplant17	Taps and showers in Patient’s rooms	Arizona
Renal transplant21	Showers and ice Machine	Belgium
Heart transplant22	Ice Machine	Denmark
General Patient Population23	Taps and showers	Connecticut
General Patient Population24	Taps and showers	Nova Scotia
General patient Population25	Ice machine	Pennsylvania
ICU patient26	Ice machine	New York
Neurosurgery patient27	Potable water	Germany
Transplant patients28	Taps and showers	Michigan
Pediatric Hematology And adult cardiac Patients29	Taps and showers	Italy
Pediatric renal Transplant30	Taps and showers	Spain
Renal and cardiac Transplant31	Taps and showers	New York
BMT patients32	Taps and showers	Israel

 

VI. Why is it important to prevent Legionella pneumonia?

Legionella pneumonia is a severe form of bacterial pneumonia with a high mortality rate that may often go unrecognized as a nosocomial pneumonia. (Note cases recognized only at autopsy in the table below.)

	Total No.	Deaths	Diagnosed at Autopsy
Bone marrow Transplant	7	4 (57%)	2
Heart Transplant	11	1 (9%)	1
Other diseases	7	7 (100%)	5
Total	25	12 (48%)	8

Note: This table is from Kool et al¹⁸

In the table above Kool et al, illustrate several key points. First, that in transplant patients Legionella pneumonia is a serious nosocomial infection with a high mortality rate. In addition, because the symptoms of this nosocomial infection are non specific, when sporadic cases of nosocomial pneumonia occur, it seems unlikely that clinicians will specifically look for Legionella with tests such as the urinary antigen test. The table illustrates the high proportion of cases that were not recognized as being Legionella related until autopsy. This data comes from the southwestern part of the U.S. at a regional transplant center that had a Legionella as a long term unrecognized resident in its complex water distribution system.¹⁸

Kool et al estimated that in the hospital depicted above that Legionella may have colonized the hospital with nosocomial transmission occurring for 17 years before a sudden increase in incidence led to recognition.¹⁸

Why is it important to prevent Legionella pneumonia?

• Legionella pneumonia is a severe form of bacterial pneumonia
• Patients are more likely to be admitted to the ICU
• Impacts the need for antibiotics and the selection of what kind of antibiotics to use
• High patient mortality.

Furthermore, several CDC Guideline on Infection Control measures now call for no Legionella to be present in hospital areas housing transplant patients.^3,4,19

In addition the Joint Commission for the Accreditation of Healthcare Organizations (JCAHO) issued a standard in 2001 requiring all JCAHO accredited facilities to have a management program to “to reduce the potential for hospital-acquired illness.” JCAHO holds health care facilities responsible for “managing pathogenic biological agents in colling towers, domestic hot water and other aerosolizing water systems” – Legionella among other bacteria are included as biological agents. The American Society for Healthcare Engineering (ASHE) recommended per this JCAHO standard that healthcare facilities conduct risk assessments of their potential sources of Legionella and develop a management pan for their water systems.¹¹ In the most recent update of standards to take go into effect in January, 2005 JCAHO has again raised the bar on infection control at hospitals to decrease hospital acquired infections including setting goals to address unprotected exposure to pathogens.² JCAHO is asking the hospital it accredits to move from standards to a “culture of safety”.²⁰

VII. What are the options and challenges for controlling Legionella contamination in Hospital water distribution systems?

First, Legionella spp persist in the optimal conditions provided in large hospital water distribution systems because they colonize the high volume hot water tanks, biofilm and live inside amoeba making chemical and physical systemic treatment challenging. The options for treatment can be systemic – directed at the entire water distribution system or focal directed at a portion of the water distribution system.

A number of methods exist for systemic treatment to manage Legionella contamination in the hospital water distribution system. These systems have variable levels of success, often providing a short term reduction in Legionella contamination only to lead to re-colonization within a few months. Legionella persists in biofilms and inside amoeba making systemic treatment far more challenging.

Method	Efficacy/Advantage	Disadvantage
Thermal eradication – Superheat and flush33	Can reduce Legionella is cheap and needs no special equipment Generally systemic treatment	Short term benefit then recolonization occurs time consuming, scalding can occur
Hyperchlorination33	Chlorine has been shown to inactivate Legionella in suspension but in biofilms and amoeba Legionella are more resistant. Generally systemic treatment	Recolonization can occur within 60 days with Legionella. Corrosive to the pipes this has prompted five major academic medical centers to abandon use
Chloride Dioxide34	Effective at higher water temperatures and Higher ph. A systemic treatment	Recolonization is likely to occur, Legionella in biofilms and amoeba may be resistant – one report shows failure to control Legionella after 18 months
UV light33	This is a focal treatment. It is easy to install and has no adverse effects on the pipes – could possibly be used closer to point of use	Unsuitable as a sole modality for a hospital especially since Legionella persist in biofilms
Copper/Silver Ionization33	A systemic treatment can kill Legionella but may still not yield no Legionella for transplant units	Long term treatment can theoretically cause resistance electrodes accumulate scale and must be regularly cleaned can impact water quality

Multiple approaches as a disinfection approach may be the method of choice to assure the level of protection required for all patients – consider point of use sterilizing grade filtrations for those areas of the hospital with high risk patients – as a means to meet the CDC challenge of no Legionella in water outlets in transplant units combined with systemic treatment.

Vonberg et al reported at SHEA their test results for the use of the Pall-Aquasafe in an ICU setting where Legionella contamination was present.³⁵ The product has now been adopted to avoid patient exposure leading to nosocomial Legionellosis.

Vonberg et al demonstrate that point-of-use filters can be used in an ICU setting to minimize patient exposure to Legionella³⁵ (Percent of samples positive for Legionella)

Point-of-use filters eliminated Legionella
Legionella concentration (CFU/mL by day of sampling)³⁶

Sample Site (Immediate Sample)*	Legionella Concentration (CFU/ml) by day of sampling
Filters	0 days	2-3 days	4 days	6-7 days	8 days
Filter #1	0	0	0	0	0
Filter #2	0	0	0	0	0
Filter #3	0	0	0	0	0
Filter #4	0	0	0	0	0
Controls
Control #1	103	303	110	75	85
Control #2	116	235	130	130	85
Control #3	11	38	137	20	25

* Data as presented by Stout at EWGLI and International Paris Workshop on Legionella

Sheffer and Stout et al evaluated the Pall-Aquasafe^® water filter in a hospital building with chronic Legionella contamination and found that point-of-use filters completely eliminated Legionella pneumophilia. The authors concluded these point-of-use filters could prevent exposure for high-risk patients to waterborne pathogens. The comparison chart below from one hospital’s experience shows that control of Legionella contamination in a hospital water distribution system is possible for the short term with some variable results with systemic treatments but provides little long-term benefit. With the results from Vonberg et al and Sheffer and Stout et al added to the chart, point-of-use filtration can provide a filter barrier at taps and showers in critical care areas of the hospital housing high risk patients such as transplant patients.

Comparison Chart of Water Disinfection Methods in a Hospital Environment³⁷

	Super Heating & Flush	Auto Chlorine (mono-chlora-mines)	Chlorine Dioxide	Cooper Silver Ionization	Ozone	UV	UV + Auto Chlorine	UV + Chlora-mine	UV + Chlorine Dioxide	Point-* of-Use Filters
Short term effective-ness against Legionella	Yes, one week	Yes	Yes, less effective than chlorine	Yes	No	No		Yes, but less than chlorine	Yes	Yes
Long term effectiveness against Legionella	None	None	Minimal until biofilm re-estab-lished	Yes but tolerance may develop	None	None	None	None	Minimal biofilm re-estab-lishes	Yes filter replace 7 days

* Note: The point-of-use filtration data was derived from data from Vonberg et al ref 35 and Sheffer and Stout et al reference 36 and not part of the original comparison chart.

VIII. Summary and Conclusions:

Legionella species are likely to be common inhabitants of hospital water distribution systems but may go unrecognized as a risk for patients for years because of lack of environmental surveillance. Legionella pneumonia is a serious nosocomial infection with a high mortality rate that may occur as sporadic cases of pneumonia and be unrecognized in the hospital setting for years.

Several CDC Guidelines call for no Legionella to pre present in hospital areas housing transplant patients.

While a number of methods exist for systemic treatment that may minimize the Legionella population in the water distribution system in the short term, re-colonization frequently occurs within a few months. Legionella can resist chemical and physical disinfection schemes by living in biofilms and inside of amoeba in the water distribution system. The best approach to minimizing patient exposure to Legionella, particularly for high risk patients who are immune suppressed such as transplant patients may be combining multiple methods such as a systemic method with point-of-use sterilizing grade filtration for critical care units such as the transplant unit. Filters are immediate in providing a barrier and have been demonstrated to be very effective in eliminating Legionella exposure at point-of-use water outlets.

Manage Patient Exposure to Waterborne Pathogens at the Point-of-Use with the Pall-Aquasafe Sterilizing Grade Filters.

References

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