Evaluation of the frequency of Legionella pneumophila ralF and lepA genes isolated from patients with respiratory infection using PCR

Legionella pneumophila is an aerobic gram-negative bacterium and etiology of legionnaires disease. The ralF and lepA genes belong to the members of type IV secretion system are essential for intracellular growth and survival of bacteria. The aim of this study was to isolate L. pneumophila from bronchoalveolar lavage (BAL) fluid samples and the frequency of lepA and ralF genes. This cross-sectional study was carried out on100 BAL fluid samples collected from the patients suffering of respiratory infections who visited Charmahal-O-Bakhtiri health centers. Isolation of L. pneumophila was performed using a specific medium (BCYE). Then, all the samples were evaluated using PCR and specific primers designed for 16S rRNA gene. Furthermore, the frequency of lepA and ralF genes was determined using PCR method. Overall, 9% of the total 100 samples were infected to L. pneumophila. Furthermore, molecular tests showed that 12 cases out of these samples were positive for this bacterium. The frequency of the ralF and lepA genes in these samples were measured 41.66 and 25%, respectively. In addition, 8.33% of the samples carried both genes. Our studies indicated high frequency of the ralF and lepA genes in L. pneumophila isolated from this area. It is possible to determine L. pneumophila in fresh samples based on PCR technique without using in media. Furthermore, PCR technique is faster and more accurate for detection of L. pneumophila in bronchoalveolar samples in comparison to culture method.