Isolation of Legionella from BAL samples of Legionella pneumonia patients, by PCR and Culture Methods

Among the members of legionellaceae, Legionella Pneumophila is involved in 95% of cases of severe pneumonia. Isolation of the causative agent from bronchoalveolar lavage (BAL) fluid specimen is a delicate process and also time-consuming. Moreover, it has been shown that some Legionella strains may be viable but cannot be cultured. The aim of this study was comparison of culture and PCR for detection of Legionella pneumophila from bronchoalveolar lavage (BAL) fluid specimens In this study, 70 BAL fluid specimens were collected from patients suspected to Legionnaires’ disease. These samples were cultured on selective buffered charcoal-yeast extract agar (BCYE) and then tested with specific L. pneumophila primers for mip gene. Among 70 BAL samples, three (4.2%) were positive with culture and six (8.4%) of specimens were positive by PCR. The three culture positive samples were all positive after specific DNA amplification. Among 63 culture-negative samples, 3 were positive after amplification. The clinical features of the patients were in accordance with legionellosis. The accurate diagnosis of Legionella pneumophila has an important implication for the treatment of infection. Analysis of the results showed that PCR is faster and more sensitive for isolation and identification of L. pneumophila to apply on BAL fluid specimens than culture. Therefore, specific Legionella PCR can be a good option for isolation and identification of Legionella pneumophila from bronchoalveolar lavage (BAL) fluid specimens in patient of severe pneumonia