Spread of Exotoxin S and Protease IV Genes and Their Correlation with Antibiotics Resistance Among the <i>Pseudomonas aeruginosa</i> Strains Isolated from Patients with Corneal Keratitis

Background: Pseudomonas aeruginosa is a leading nosocomial pathogen. Its complex virulence mechanisms and rapid adaptation to drugs/antimicrobials are well known. Objectives: In this work, we searched for exotoxin S (exoS) and protease IV (piv) genes in P. aeruginosa resistant strains from corneal keratitis patients. Methods: Pseudomonas aeruginosa strains were isolated by taking samples from the eyes of patients with keratitis and cultured on McConkey and Citrimide, followed by biochemical tests. Then, exoS and piv genes were identified through the PCR process. Bacterial resistance to imipenem, piperacillin, ciprofloxacin, tobramycin, ceftazidime, gentamicin, ticarcillin, amikacin, and cefixime was measured via the disc diffusion test. Finally, logistic regression analysis was performed using SPSS V23. Results: Out of the entire set of ocular specimens, 72 isolates (41.14%) exhibited positive culture results. Among culture-positive isolates, 15 (20.83%) were identified as P. aeruginosa via biochemical tests. The results showed resistance to imipenem, piperacillin, ciprofloxacin, tobramycin, ceftazidime, gentamicin, ticarcillin, amikacin, and cefixime in 66.7%, 60%, 66.7%, 80%, 46.7%, 53.3%, 80%, 53.3%, and 93.3%, respectively. The prevalence of exoS and piv genes was 53.3% and 86.7%, respectively. The findings of our study demonstrate a significant correlation between the exoS gene and individual resistance to ceftazidime and gentamicin agents. No significant correlation between the piv gene and antibiotic resistance was observed. Conclusions: The prevalence of multi-drug resistance among P. aeruginosa strains obtained from patients with keratitis was found to be 86.66%. This finding underscores the need to identify novel drug compounds for these bacteria and modify antibiotic consumption patterns within this specific geographic region. The piv gene is present in the majority of keratitis strains, suggesting its significance in the pathogenicity of the bacteria. The identification of piv and exotoxin inhibitors can also provide assistance. The exoS-gentamicin/ceftazidime link is the key novel finding of this study.