Screening of lasl and lasR Genes in Clinical Isolates of Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa is a ubiquitous Gram-negative bacillus which causes variety of clinical illnesses in both humans and animals. It is practically hard to eradicate this pathogen from hospitals due to its remarkable potential for adaption to unfavorable environmental conditions. Quorum sensing system is a density-based communication mechanism that allows bacteria to communicate with one another. P. aeruginosa has four types of quorum sensing systems las, rhi, pseudomonas quinolone signal ( PQS ) and integrated quorum sensing system. Our study focused on the las system among the four systems of quorum sensing. We began our research by detecting phenotypic expression of QS las system by assaying biofilm formation, PYA production, protease production and elastase production in clinical P. aeruginosa isolates in order to understand QS and its controlled virulence factor expression. After that, the genotypic assay was done to examine the prevalence of QS las genes i.e las! and las R genes. So we determined the QS regulated virulence factors and correlated to the presence of Las system. Sensitivity testing for antibiotics were also carried out. In this study we use 175 isolates of Pseudomonas aeruginosa collected from the Armed Forces Institute of Pathology (AFIP). For the identification of P. aeruginosa strains in the samples each sample has undergone through multiple tests like morpho-cultural, biochemical, and molecular techniques. The biofilm ability of all 175 P. aeruginosa isolates was tested. Biofilm formers were 95.43% (8.57 %, 60.57%, 26.29% strong, moderate and weak biofilm formers), whereas non-biofilm formers were 4.57%. Protease producers were 91 % , pyocyanin producers were 74% , elastase producers were 60 %. A peR assay was used to identify the las QS system and las! and lasR genes. According to the findings, 90 % have las system genes. lasR gene was found in 52 % of the isolates and las! was found in 71 % of the isolates. The las QS system genes were found in 77% of pyocyanin producers, 93% of the protease producers and 89% of elastase producers. Two QS las genes and associated virulence factors are found in a large number of P. aeruginosa isolates. There was a correlation between them as well. As quorum sensing is essential for the expression of a battery of virulence factors as well as for biofilm formation in P. aeruginosa thus the results of my research suggest that the inhibition of QS regulatory process would be effective for removing and reducing the drug resistance.