Pulsed field electrophoresis of genomic restriction fragments for the detection of nosocomial Legionella pneumophila in hospital water supplies.

Ten Legionella pneumophila strains isolated from different sources were analyzed according to their restriction fragment patterns obtained by cleavage of genomic DNA with NotI and SfiI and separation by pulsed field electrophoresis. Three L. pneumophila isolates from a nosocomial outbreak in Lübeck (Germany) and three other L. pneumophila strains independently isolated from a water tap located in the care unit where the patients were hospitalized exhibited identical restriction fragment profiles. Therefore, we concluded that these environmental specimens were the source of the Legionnaires disease. Another two isolates from patients and two strains from the environment, all unrelated to the outbreak described, showed different cleavage patterns.