Legionella Bacteria Tied to Legionnaires’ Disease

April 15, 2013- A strain of Legionella bacteria that caused the recent fatal outbreak of Legionnaires’ disease in a Pittsburgh-area Veteran’s Affairs hospital was nearly identical to the bug responsible for a lethal outbreak there in 1982. Centers for Disease Control (CDC) investigators described the strain as a granddaughter or grandson of the 1982 strain.

The strain likely persisted over time in the hospital’s drinking (potable) water system, despite decades of hot-water flushes, cycles of chemical disinfectant, and the installation of a copper-silver ionization system designed to kill it, according to a Feb. 26 report in ProMED Digest.

It’s believed that the bug persisted in pipes, trapped in thin layers of microorganisms called biofilms. (Read more about biofilms at the end of this article.) The chief of the Allegheny County Health Department lamented that the recent outbreak points to the need for national standards to monitor and treat water-distribution systems in health care facilities. 

Unfortunately, there is not a national standard that directs how to minimize the problem, according to the Health Department. The report also cites the need for aggressive monitoring for Legionella, including testing hospital water systems, even if the disease is not identified in patients.

Biofilms are ubiquitous. Nearly every species of microorganism, not only bacteria and archaea, have mechanisms by which they can adhere to surfaces and to each other. Biofilms will form on virtually every non-shedding surface in a non-sterile aqueous (or very humid) environment. Biofilms allow these organisms to persist and thrive in many environments, including:

  • Biofilms can be found on rocks and pebbles at the bottom of most streams or rivers, and they often form on the surface of stagnant pools of water. In fact, biofilms are important components of food chains in rivers and streams and are grazed by the aquatic invertebrates upon which many fish feed.
  • Biofilms can grow in the most extreme environments, from the hot, briny waters of hot springs to frozen glaciers, and in environments that range from the very acidic to very alkaline.
  • In the human environment, biofilms can grow in showers easily since they provide a moist, warm environment. Biofilms can form inside water and sewage pipes and cause clogging and corrosion. Biofilms on floors and counters can make sanitation difficult in food-preparation areas.

Organisms in biofilms are relatively protected from temperature and chemical disinfectants. Periodically, organisms are released by the biofilm, after which they are present in the water supply and infect people exposed to aerosols. These properties are what make them notoriously hard to eradicate from a water system and a danger to those who use the water. 

For more information on biofilms

--Co-authored by Dr. Conibear and John Dobby of Carnow, Conibear & Assoc. CCA can assist clients in performing proactive monitoring for Legionella bacteria in water distribution systems and has provided such services for facility managers responsible for maintaining high-rise office buildings, industrial, health care, and school facilities. Carnow Conibear has also assisted with remediation following outbreaks.

For further information, contact, John Dobby, CIH, CSP at jdobby@ccaltd.com, 312-762-2912

Carnow Conibear and Associates is a demonstrated leader in the occupational and environmental health professions since 1975. To find out more, click here or call us at (800) 860-4486.