Examining Exotoxin Virulence Factor and Fosfomycin Antibiotic Resistance Genes in Pseudomonas aeruginosa Causing Eye Infections

Pseudomonas aeruginosa is considered as an important opportunistic bacterial pathogen associated with nosocomial infections. Therefore, it is important to identify this bacterium in clinical samples and report the results to health authorities. The aim of this study was the molecular identification of some virulence factors and fosfomycin resistance genes in P. aeruginosa strains.

A total of 100 P. aeruginosa strains were isolated from clinical samples of patients with eye infections in three distinct laboratories in Tehran hospitals (Pars, Milad, and Motahari). The antibiogram of all isolates against eight antibiotics was determined by standard Kirby-Bauer disk diffusion method. Then DNA was extracted from the isolates, and the frequency of exoY, exoT, exoU, exoS, fosC, fosB, and fosA genes was evaluated by multiplex PCR (polymerase chain reaction).

The highest resistance was observed to cotrimoxazole (85%), ceftazidime (83%), cefotaxime (79%), and cefepime (72%), and the highest sensitivity was observed to ciprofloxacin (55%), gentamicin (52%), and piperacillin (41%), respectively. Out of 60 investigated isolates, 58 isolates were positive for exoY, exoT, and exoU, while only four isolates were exoS positive. In addition, one strain (1.66%) had the fosC gene, two strains (3.33%) had the fosB gene, and 12 strains (20.02%) had the fosA gene.

The results showed that the frequency of fosfomycin resistance genes, whose protein product modifies the epoxide group of fosfomycin and reduces the effectiveness of this antibiotic, was significantly low in the investigated strains.