The Study of Frequency of SIM and AmpC Genes in Clinical Isolates of Pseudomonas aeruginosa in Gilan, Iran

This study aimed to determine the antibiotic resistance pattern of Pseudomonas aeruginosa clinical isolates and the frequency of blaSIM and blaAmpC genes in resistant strains.

In this cross-sectional study, 94 P. aeruginosa isolates were collected from the burn wards of Gilan province hospitals in 2018 and identified by biochemical methods. Strains producing β-lactamases and metallo-β-lactamases were detected by two

disk diffusion method and antibiotic resistance method in combination with disk diffusion method, respectively. The presence of blaSIM and blaAmpC genes in the resistant strains was investigated using PCR, and data analysis was performed.

Based on the obtained results, colistin was identified as the most effective antibiotic with a resistance rate of 27.7%, and the highest antibiotic resistance was observed against trimethoprim/sulfomethoxazole (83%). In the phenotypic test of 94 samples, 29 (30.9%) carbapenemase-producing isolates and 33 (35.1%) β-lactamase-producing isolates were identified. Based on the PCR results, among 44 (46.8%) samples containing β-lactamase and carbapenemase enzymes, the frequency of blaSIM gene was 9.1% (4 of 44, and 4.3% in all the studied isolates), and the frequency of blaAmpC gene was 15.9% (7 of 44, and 7.4% in the all studied isolates).

The results of this study indicated a high prevalence of drug resistance in clinical isolates of P. aeruginosa. In particular, there was an increasing rate of resistance to beta-lactam antibiotics, and the presence of MBL and ESBL associated genes was considerable, which limit the choice of suitable treatment for patients with severe infections.