The causative agent of legionellosis, Legionella pneumophila, colonizes all natural and human-made water networks, thus constituting the source of contaminated aerosols responsible for airborne human infections. Efficient control of infections, especially during epidemics, necessitates the fastest and most resolutive identification possible of the bacterial source for subsequent disinfection of reservoirs. We thus compared recognized typing approaches for Legionella with a method based on characterization of insertion sequence ( Moreover, specific ISLpn11 copies were found only in strains isolated from particular cities. In more than half of the cases, each clinical isolate had an ISLpn11 profile that was recovered in at least one environmental isolate from the same geographical location, suggesting that our method could identify the infection source. Phylogenetic analysis suggests a clonal expansion for the L. pneumophila Paris strain.

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