Is molecular typing of isolates a valuable tool to prioritize environmental interventions to prevent nosocomial legionellosis?

Although cases of legionella pneumonia are increasingly recognized, there is no general consensus regarding the prevention of legionellosis in hospials. A cluster of two cases of Legionella pneumophila serogroup 1 occurred over 4-week period in the teaching hospital of Sapienza University of Rome, Italy. A number of measures were undertaken to control the situation, including extensive environmental monitoring for legionellae and decontamination of the hospital water system with hyperchlorination and installation of sterilizing filters at water taps. The results of this study show clearly that the virulence of environmental isolates of Legionella play a greater role for the risk of nosocomial legionellosis than the level of water contamination or the proportion of positive sample sites.