Evaluation of Antibiotic Resistance Pattern and Extended-Spectrum Beta-lactamases in Pseudomonas aeruginosa Isolates Obtained from Clinical Samples by Phenotypic and Genotypic Methods in Zabol, Iran

Background: Pseudomonas aeruginosa is a human opportunistic pathogen that is known to be responsible for various diseases. However, its antibiotic-resistant isolates often cause serious infections. Methods: This study for the first time investigated a total of 80 P. aeruginosa isolates collected from patients admitted to Amir Al-Momenin hospital. The isolates were identified by biochemical assays. The combination disc test method was used to measure antibiotic susceptibility and confirm the presence of extended spectrum-beta lactamases-producing enzymes. Also, the presence of enzyme-producing genes bla CTXM-1, bla CTXM-2, bla CTXM-3, bla SHV, and bla OXA of the target enzymes was examined using polymerase chain reaction. Results: Out of 80 P. aeruginosa isolates, 32 isolates (40%) were beta-lactamase generators. Resistance to the studied antibiotics was found to be 97.5%, 90%, 81.3%, 75%, 75%, 72.5%, 60%, 52.5%, 50%, 32.5%, 28.8%, and 0% for amoxicillin, amoxiclav cephalexin, nitrofurantoin, cotrimoxazole, azithromycin, ceftriaxone, cefotaxime, gentamicin, ceftazidime, ciprofloxacin, and imipenem, respectively. Therefore, the highest antibiotic resistance was against amoxicillin, co-amoxiclav, and cephalexin, respectively, while the lowest was detected for imipenem. Besides, 17.5% of the studied isolates were multidrug-resistant (MDR). Among extended-spectrum beta-lactamases-producing genes, bla CTXM-3 displayed the highest frequency of 84.4%. Conclusion: The findings demonstrated the wide resistance of P. aeruginosa isolates against various antibiotic classes. According to the results, it is suggested to identify different patterns of antibiotic resistance of P. aeruginosa isolates prior to the onset of treatment for any P. aeruginosa-related infections.