Loop-mediated isothermal amplification for detection of Legionella pneumophila in respiratory specimens of hospitalized patients in Ahvaz, southwest Iran

Background: Legionnaires' disease is an important public health problem that can cause substantial mortality and morbidity. Legionnaires' disease-risk estimation may be compromised by uncertainties in Legionella-detection methods. The aim of this study was the detection of L. pneumophila in respiratory specimens of hospitalized patients with respiratory symptoms by culture, PCR, and loop-mediated isothermal amplification (LAMP) methods. Methods: Sputum and bronchoalveolar lavage samples were obtained from patients with pneumonia admitted to teaching hospitals in Ahvaz, Iran from June 2016 to March 2017. Isolation of Legionella spp. was done by culturing the samples directly onto buffered charcoal-yeast extract and modified Wadowsky-Yee agar medium. Then, PCR and LAMP assays were performed for detection of L. pneumophila via its mip gene in respiratory specimens. Results: A total of 100 respiratory specimens were collected. Our results showed that 1% of the samples were culture positive for Legionella spp., and 3% and 7% of samples were positive for L. pneumophila using the mip gene on PCR and LAMP assays, respectively. Conclusion: Legionnaires' disease should be considered in the diagnosis of pulmonary infectious diseases. Also, the LAMP assay is a faster method with higher sensitivity and specificity than conventional methods, such as PCR and culture, for laboratory diagnosis of Legionnaires' disease.