Molecular Epidemiology of Legionellosis in Grenoble Region

Patients admitted to Grenoble University Hospital between 2006 and 2011 for severe legionellosis were retrospectively included in the study.

Clinical, epidemiological, diagnostic and prognostic data of these patients were recorded retrospectively.

Lower respiratory samples collected from these patients on a routine basis for microbiological analysis, especially Legionella culture, were tested using traditional microbiological methods. The remaining part of these samples was stored at -80°C fur further molecular analyses.

The molecular tools developed by our bacteriology laboratory included the following: a real-time polymerase chain reaction (qPCR) test allowing detection and differentiation of L. pneumophila and other Legionella species; a qPCR test allowing determination of the Legionella DNA load in lower respiratory samples; a qPCR allowing detection of gyrA (the gene encoding subunit A of DNA gyrase) mutations that the investigators previously determined to be correlated with fluoroquinolones resistance in L. pneumophila; a high-throughput sequencing approach allowing confirmation of gyrA mutations and determination of the percentage of mutated alleles.

The microbiological data, especially those obtained with the developped molecular tools, were tentatively correlated with the severity and outcome of infection in our patients' cohort.