Efficient isolation and virulence characterization of Legionella pneumophila: Insights from a wide variety of water sources in Bangladesh

Several members of the Legionellaceae family are increasingly recognized as a causative agent of sporadic community-acquired atypical cases of pneumonia. Alarmingly high mortality and no effective antimicrobials necessitate accurate detection of this fastidious organism, specifically from the environment considering Legionella mostly transmit through contaminated water or moist soils. In this study, we have utilized a combination of molecular and culture based protocols to detect and characterize virulence genes in Legionella pneumophila from various water sources in Bangladesh. Out of 198 water samples, 28.8 % were PCR positive for Legionella spp. Among these, 43.9 % were non-pneumophila and 56.1 % were L. pneumophila. In terms of season and source, 21.4 % of the late autumn and 38.5 % of the tap water samples were predominantly positive for L. pneumophila. Our culture method demonstrated an 84.4 % recovery rate for L. pneumophila, of which 27 representative isolates were chosen for virulence characterization using 21 genes categorized into 7 groups. Group 1-6 genes responsible for a broad spectrum of virulence traits were majorly found within the isolates, however, group 7 responsible for severe human infections were comparatively less prevalent. Virulence gene profiling showed two isolates containing 19/21 genes were isolated during summer/late autumn from hot water/tap water. Statistical stacked plots found a significant association between group 7 virulence factors with summer and warm water isolates. Our findings necessitate heightened surveillance for this organism through incorporating routine water monitoring plans in similar environmental settings worldwide.