Comparative Distribution of Type III Secretion System Effector Genes in Clinical and Food-Associated Pseudomonas aeruginosa Isolates from Baghdad, Iraq

Pseudomonas aeruginosa bacteria are known to produce several proteins (toxins) that serve as critical virulence factors. There are currently four known effective toxins secreted via the type III secretion system (T3SS): exoS, exoT, exoU, and exoY. Rarely do all of these poisons occur in a single strain. In this investigation, 90 P. aeruginosa isolates were analyzed, comprising 50 clinical samples from hospital environment and 40 food-associated isolates from community dietary reservoirs. Using PCR, the toxin genes exoT, exoY, exoU, and exoS were successfully identified. The concentration and purity of genomic DNA samples were determined by spectrophotometry (nanodrop) and agarose gel electrophoresis. exoT, exoS , exoY, and exoU gene distribution frequencies were found to be 96.7%, 83.3%, 81.1% and 22.2%, respectively, among all isolates. According to statistics, both the highly cytotoxic exoU gene (32.0% vs. 10.0%, (P = 0.0203) and the exoY gene (90% vs. 70.0%, P=0.0282) significantly preferred clinical compartments over food matrices. Additionally, genotype distribution analysis showed that all 16 exoU-positive clinical isolates and two food-associated isolates (5.0%) concurrently carried the exoS gene, indicating the existence of the exoS +/exoU+ genotype in nearby reservoirs. These findings demonstrate how T3SS genetic markers are distributed in clinical and food-related settings in Baghdad.