Detection Of virulence factor genes in isolated Legionellapneumophila isolates from hospital water sources

Background and Aim : Owing to the fact that Legionella presence in water sources does notnecessarily lead to onset of disease, several factors such as inhaled bacteria dose, virulence factorsand diversity of serogroups can be considered as contributing factors. The main aims of this studywas to Using culture for Legionella monitoring in hospital water samples, risk assessment by aninvasion of the HeLa cell and investigate the presence of major virulence factor genes as well asthe ability to form biofilms in the Legionella isolates.Methods : In this study ۱۰۰ water samples collected from hospitals of Iran university medicalsciences, from water sources and were examined. All samples were treated with acid. Then theywere cultures on selective media such as GVPC. To confirm the primary identity of the isolatescolonies, gram staining and lack of growth after insemination to conventional laboratoryenvironments such as blood agar and BCYE without L-CYS. Using Favor gene kit, DNA of thesamples was extracted, and then the PCR reaction for ۱۶srRNA genes was done using proprietaryprimers. Virulence genes (mip, rtx, lvh, dot, hsp۶۰) and biofilm formation were subsequentlyanalyzed among the isolated Legionella pneumophilaResults : Out of water samples, ۱۲ cases (۱۲%) were positive by culture method and ۴۲ cases(۴۲%) were positive by the PCR method and results of culture were confirmed. Quantification ofbacteria in ۲۳ cases (۵۴/۵۶%) were with ۱۰۴GU/L and ۲ cases (۴/۷۶%) were with <۱۰۴ GU/L.PCR assay for the virulence genes showed that all ۱۲ (۱۰۰%) isolates were positive for mip genes,۹ (۷۵%) were positive for dot gene, ۸ (۶۶.۶۶%) were positive for hsp, ۶ (۵۰%) were positive forlvh, and ۴(۳۳.۳۳%) for rtx. Two of the isolates displayed higher ability to form biofilm in referenceto the standard strain.Conclusion : This study reveal that water sources in hospital colonized by virulent legionella andshould be continuously monitored to avoid elevated concentration of legionella and visible biofilmformation.

کلیدواژه ها:

Legionella pneumophila ، rtx ، dot ، hsp۶۰ ، mip ، lvh ، ۱۶srRNA ، biofilm formation ، virulence genes ، PCR ، Realtime PCR ، invasion