An investigation of type 3 secretion toxins encoding-genes of Pseudomonas aeruginosa isolates in a University Hospital in Egypt

Abstract

Objective: Pseudomonas aeruginosa uses type 3 secretion system (T3SS) to directly inject four toxins into host cells. The aim of the study was to determine the prevalence of the toxins-encoding genes among P. aeruginosa isolates collected from nosocomial infections and environmental sources. Methods: Clonal relatedness of the studied P. aeruginosa isolates (n=85) was studied by RAPD typing. Multiplex PCR was performed on the 85 P. aeruginosa isolates (68 nosocomial isolates obtained from hospitalized patients present in different wards and departments, and 17 environmental isolates including 2 isolates from health-care worker hands from ICU) to detect the secretion toxins-encoding genes. Results: RAPD fingerprinting demonstrated that most strains were of distinct genotypes and determined the presence of 54 RAPD patterns. The prevalence of the genes among all isolates was as follows; exoT-100%, exoS- 40%, exoY- 83.5% and exoU- 62.4%. No significant differences in the prevalence of these genes were observed between nosocomial and environmental isolates or between isolates cultured from different sites of infection. The part of P. aeruginosa strains harboring either exoS (37.6%) or exoU (60%) gene was significantly higher (P<0.001) than that contained both genes (2.4%). Conclusion: ExoT was present in all isolates and exoS, exoY and exoU are variable traits with exoU gene was the third in prevalence after exoT and exoY. No significant differences in exoS, exoY and exoU prevalence were observed between nosocomial and environmental isolates or between isolates from different sites of infection. ExoS and exoU genes were mutually exclusive that almost all isolates contain either exoS without exoU or exoU without exoS. J Microbiol Infect Dis 2013; 3(3): 116-122