Evaluation of Legionella PCR Techniques for the Routine Diagnosis of Legionellosis

The validity of molecular techniques for the diagnosis of legionellosis is not known. Although PCR can detect Legionella pneumophila (responsible for 80% of legionellosis) and other Legionella species, this test is not recommended in standard guidelines to assess this diagnostic, by contrast to culture of sputum, serology and urine antigen. The aim of this study is to evaluate Legionella PCR techniques, performed directly onto the sputum aspirates, for the routine diagnosis of pneumonia in adults' patients admitted to hospital. This study implicates 3 University hospitals (Lyon, Grenoble and Saint-Etienne) in collaboration with the French reference center of legionellosis for a previous duration of one year. In addition to the usual diagnostic tests that are performed when pneumonia is suspected, real-time PCR will be added for the detection and differentiation of Legionella. Hypothesizing the inclusion of 1000 pneumonia in this study, the predictable number of newly-detected legionellosis will be approximately 60 to 70 cases. According to a predefined algorithm, cases of legionellosis will be classified as definite or probable. Sensitivity and specificity of the real-time PCR will be calculated according to this classification. This study is intended to validate real-time PCR as a tool for the rapid diagnosis of legionellosis, allowing to optimize the antibiotic treatment of pneumonia. PCR techniques can also contribute to the better detection and differentiation of Legionella sp infections that are not documented accurately by routine microbiologic tests.