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February 2011: New Method Facilitates Detection of Pathogenic Legionella Bacteria in Water

Monday, February 28, 2011

February 2011: New Method Facilitates Detection of Pathogenic Legionella Bacteria in Water

Dangerous Showers… Hot water heaters, air conditioning or showers are a true paradise for Legionella. Some strains of these bacteria are highly infectious for humans. Transmission occurs mostly via pathogen-containing aerosols. A verification of the different types of Legionella is very complicated since the bacteria are difficult to isolate and to cultivate. Furthermore, subtypes make a reliable detection even harder: the species Legionella pneumophila alone, cause of severe pneumonias in immunocompromised patients, includes 14 subtypes.

Researchers at the German Helmholtz Centre for Infection Research in Braunschweig (Helmholtz-Zentrum für Infektionsforschung, HZI) have now developed a highly accurate and fast diagnostic tool to detect and distinguish different L. pneumophila subtypes on the molecular level. The bacterial DNA is isolated directly out of the water sample, purified and analyzed. “Until now, this has not been possible,” says Dr. Manfred Höfle, Head of the “Molecular Diagnostics Laboratory” at the HZI. The method uses small, repeating DNA sections (so-called tandem repeats) that are very characteristic for each L. pneumophila strain and subtype. “We mark those tandem repeats with dyes. Each bacterial strain provides us with a characteristic pattern. Thus we can not only verify which pathogen is in the sample, but can also check its potential virulence.”

This new method has the potential to facilitate the risk management of drinking water supply systems: It may help to detect contaminated areas and control growth in biofilm harboring pathogenic Legionella populations.