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 secretion toxins into host cells. The aim of the study was to determine the prevalence of thee secretion 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 %). Concolusion: 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 cultured from different sites of infection. ExoS and exoU genes are mutually exclusive that almost all isolates contain either of both genes not both.

Keywords

• Pseudomonas aeruginosa, type 3 secretion toxins, multiplex PCR

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

Öz

Amaç: Pseudomonas aeruginosa tip 3 sekresyon sistemiyle (T3SS ) direk dokuya salınan 4 sekretuar toksin kullanır. Bu çalışmanın amacı hastane enfeksiyonlarından ve çevresel kaynaklardan izole edilen P. aeruginosa izolatlarında sekretuar toksin kodlayan üç genin prevalansını saptamaktır. Yöntemler: Çalışılan P. aeruginosa izolatlarının klonal yakınlığı RAPD tiplendirme metodu ile bakılmıştır. Sekretuar toksin kodlayan genleri saptamak için 85 P. aeruginosa izolatında (farklı klinik ve bölümlerde yatan hastalardan izole edilen 68 hastane kaynaklı izolatı ve ikisi yoğun bakım ünitesindeki sağlık çalışanının ellerinden izole edilen 17 çevresel izolat) multiplex PCR çalışıldı. Bulgular: RAPD fingerprint analizi ile varlığı tespit edilen 54 RAPD paterninin varlığı suşların çoğunun uzak genotiplere sahip olduğunu gösterdi. Tüm izolatlarda saptanan genlerin prevalansı sırasıyla exoT (% 100), exoS (% 40), exoY (% 83,5) ve exoU (% 62,4) şeklindeydi. Farklı enfeksiyon bölgelerinden üretilen izolatlar arasında yada hastane ve çevresel kaynaklardan elde edilen izolatlar arasında bu genlerin prevalansı açısından anlamlı bir fark yoktu. P. aeruginosa suşlarından exoS (% 37,6) veya exoU (% 60) genlerinden birini taşıyanlar her iki geni taşıyanlardan (% 2,4) anlamlı olarak daha fazlaydı (p<0.001). Sonuç: ExoT tüm izolatlarda bulunurken exoS, exoY ve exoU genlerinin varlığı değişkenlik gösteriyordu. ExoU geni exoT ve exoY geninden sonra üçüncü sıklıkta görülmekteydi. exoS, ExoY ve exoU görülme prevalansı hastane kaynaklı ve çevre kaynaklı suşlar arasında veya değişik bölge veya enfeksiyonlar arasında anlamlı bir farklılık göstermedi. ExoS ve exoU genleri hemen tüm izolatlarda ya birlikte bulunmakta veya iki de bulunmamakta idiler

Anahtar Kelimeler

• Pseudomonas aeruginosa, type-3 sekresyon toksinleri, multiplex PCR

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