Legionella pneumophila in water [M200] NEW!
Published: July 8th, 2009
Revised: October 4th, 2009
The Gram negative bacterium Legionella pneumophila is a common environmental cause of pneumonia, often associated with institutional outbreaks and environmental exposures. Legionella pneumophila is an endosymbiont of single celled protozoa that live in warm, stagnant water, particularly around temperatures of 30-40 °C. Building systems such as humidifiers and evaporative coolers may become contaminated by Legionella species including L. pneumophila if maintenance practices lapse or in the event of mechanical failures. Certain types of domestic hot water systems may also become affected. Most susceptible are systems in which untreated cold water is mixed with hot water downstream of the heating unit, usually as a means to prevent scalding at the faucet.
Most methods for testing fluids for L. pneumophila rely on culture. Although culture-based methods remain the current gold-standard means of determining the presence of this bacterium, this technique has poor sensitivity (negative results cannot reliably predict the absence of contamination), and they typically require 10-14 d to complete testing. A PCR-based genetic test has been devised to detect the presence of L. pneumophila in fluid samples. This method has been extensively validated, and has been used widely in Europe for several years. This test has the advantage of much greater sensitivity coupled with the potential to provide results in as little as 4 hr, depending on the service option requested. The downside of the test is that it cannot differentiate between active colonization and residual DNA from dead cells. Nevertheless, this DNA test provides a rapid, highly conservative screen for this important pathogen as a means to guide public health intervention. Results of the test are reported as L. pneumophila genomes per litre of fluid (Genome Units/L). We do not provide this test for the evaluation of the fitness of potable water for consumption.
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