Molecular Detection Of Legionella Pneumophila Within Culture-Negative Samples

Document Type : Original Article


Biodefence Research Center, Medical Sciences Baqyalollah University Tehran, Iran


Introduction: L. pneumophila is the most important cause of legionaires, disease, which is currently reported either as a nosocomial or community acquired infection. Rapid and reliable diagnosis of legionella has hampered the epidemiological studies and disease control activities. In spite of good sensitivity and specificity, the culture method encountered serious shortcomings. Polymerase chain reaction (PCR) has been used to detect the viable but non-culturable legionella. In the present investigation, the efficacy and accuracy of mip gene based primers were tested in PCR for culture-negative samples.
Materials and Methods: The samples used in this investigation were previously reported as negative by means of conventional culture methods. DNA extraction was carried out by freezing-boiling method. The small fragment of mip gene (of L. pneumophila) was used for the primer set (LEG 1 and LEG-2) in PCR, and also for specific probe LEG-3 in southern blot. Results: From 32 culture-negative samples subjected to these primer sets, L. pneumophila DNA was detected in 6 samples. System accuracy was then checked by dot blot hybridization.
Conclusion: The results of this investigation indicated that the PCR method, with suitable primer set and probe, detects the viable but non-culturable Legionella in clinical and environmental samples.