Monday, October 21, 2019

Legionella Bacteria Persists at St. Elizabeths

On Friday, the Washington Post reported that St. Elizabeths Hospital in Southeast Washington DC remains without water after more than 3 weeks. During routine testing on September 26th legionella bacteria was found in the water of the Washington DC psychiatric hospital that occupies St. Elizabeths East Campus. Legionella bacteria which can cause Legionnaires’ disease, and pseudomonas bacteria, which can cause severe infections in people with weakened immune systems were both found in the water.

Legionella is an opportunistic pathogen that is widespread in the environment. The major sources of Legionnaires’ disease are the potable water systems of large buildings including hospitals, nursing homes, and hotels. Legionella is a common cause of hospital-acquired pneumonia, especially for immune system compromised patients. Cooling towers were originally thought to be the main reservoir for Legionella, but subsequent studies have identified the water distribution systems as the major source of legionella disease in hospitals.(1-2)

Washington Post reported that even after super chlorination of the water system, test results showed evidence the legionella bacteria remained in the system; and the water system was being retreated on Friday and over the weekend. I know it sounds as if the super chlorination was improperly done, but legionella contamination of a healthcare facility is extremely difficult to remediate. Studies have found over and over again that it is incredibly difficult to achieve enduring disinfection of hospitals.

Biofilms of water distribution systems and points of use have long been recognized as a rich environment for growth of Legionella, mycobacteria, Pseudomonas, and other waterborne organisms. Eliminating biofilms and the pathogens residing in the biofilm is a major challenge. Organisms dwelling in these environments have been found to be especially impervious to chlorination and other disinfectants. 

Biofilms occur in the pipes, sink aerators, shower heads, water fountains and other points of use. Stagnation often present in older pipe designs promotes the ideal conditions for biofilm formation. Newer guidelines for hospital construction recommend against water pipe design with dead legs and long, horizontal runs and practices (such as intermittent water usage leading to low flow) that contribute to stagnation. St. Elizabeths predates these recommendations, and convoluted pipe architecture may render their structures more vulnerable to water system colonization with Legionella. Cooling towers have also been implicated in several outbreaks. Water can also stagnate at the points of use; colonization of fixtures such as electronic eye faucets, aerators, sink drainage pipes, ice machines, decorative fountains [3,4, 5, 6, 7], and others, has been reported, and some implicated in nosocomial transmission.

Overall there is no one method  of remediation that has proven successful in all cases. However, a growing body of data supports the effectiveness of monochloramine over other disinfectants for Legionella control. Chloramination is used widely in municipal water systems including the Washington Aqueduct that supplies potable water to DC Water, but there are insufficient data on its supplemental use in hospitals. Combining disinfection with heat treatment may be the most effective treatment (8). Legionella grow within amoebae and tolerate a wide range of temperatures. Legionella replicate between 20°C and 50°C. Temperatures above 60°C are highly effective at suppressing (but not eradicating) Legionella and do so within minutes. Studies done in Tiwan indicate that heat flushing disinfection at 70°C is the most effective treatment. Let’s hope whatever method is being used for the re-treatment of the water system works. It is unacceptable to have the incarcerated residents of the psychiatric hospital without running water for basic hygiene for over 3 weeks.

Microbial contamination of a healthcare facility water supply is better prevented than remediated. Many waterborne infections are preventable with strict adherence to optimal healthcare hygiene practices and water system procedures. Hospitals must have a water management program that are updated regularly and include regular cleaning and maintenance of water outlets to avoid contamination. So, once St. Elizabeths fixes this outbreak they should institute a robust water management program. 

The hospital facility that occupies St. Elizabeths East campus is supplied by a separate water tower and on a different loop than the water for the West Campus buildings occupied by the Department of Homeland Security which was found to be free of Legionella. So the problem is within the East campus and water tower.


1. Yu PY, Lin YE, Lin WR, Shih HY, Chuang YC, Ben RJ, Huang WK, Chen YS, Liu YC, Chang FY, Yen MY, Liu CC, Ko WC, Lin HH, Shi ZY. The high prevalence of Legionella pneumophila contamination in hospital potable water systems in Taiwan: implications for hospital infection control in Asia. Int J Infect Dis 2008;12:416-420.

2. Yu VL, Beam Jr TR, Lumish RM, Vickers RM, Fleming J, McDermott C, et al. Routine culturing for Legionella in the hospital environment may be a good idea: a three-hospital prospective study. AmJ Med Sci 1987;294:97—9.

3. Davies D. Understanding biofilm resistance to antibacterial agents. Nat Rev Drug Discov. 2003;2(2):114–22.

4. Simoes M, Simoes LC, Vieira MJ. Species association increases biofilm resistance to chemical and mechanical treatments. Water Res. 2009;43(1):229–37.

5. Vergara-Lopez S, et al. Wastewater drainage system as an occult reservoir in a protracted clonal outbreak due to metallo-beta-lactamase-producing Klebsiella oxytoca. Clin Microbiol Infect. 2013;19(11):E490–8.

6. Halabi M, et al. Non-touch fittings in hospitals: a possible source of Pseudomonas aeruginosa and Legionella spp. J Hosp Infect. 2001;49(2):117–21.

7. Sydnor ER, BG, Gimburg A, Cosgrove SE, Perl TM, Maragakis LL. Electronic-eye faucets: Legionella species contamination in healthcare settings. Infect Control Hosp Epidemiol. 2012;33(3):235–240.

8. Marchesi et. al. monitored Legionella contamination of water in three hospital buildings (two occupied by patients) for three years,

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