Abstract

Pseudomonas aeruginosa is an opportunistic human pathogen which causes serious problems especially in people who have immunodeficiency. Recently, β-lactamase resistance in this bacterium has led some difficulties in treating bacterial infections. One of resistance mechanisms is production of metallo-β-lactamase (MBL). The aim of this study was to determine prevalence of imipenem-resistant P. aeruginosa carrying MBL genes.108 P. aeruginosa strains were obtained. Antibiotic susceptibility test was done by agar disk diffusion method. Minimum inhibitory concentration (MIC) was done by broth microdilution for imipenem-resistant strains. Then, EDTA-IMP test was carried out for screening MBL production in imipenem-resistant strains. Finally, polymerase chain reaction (PCR) was performed by Duplex-PCR to detect MBL genes including bla_VIM-1, bla_VIM-2, bla_IMP-1, bla_IMP-2 and bla_SPM-1 in imipenem-resistant strains. Among 108 P. aeruginosa strains, 40 (37%) strains were showed to be resistant to imipenem, MIC results determined 30 out of 40 (75%) were resistant to imipenem (MIC ≥ 16 µg/ml). EDTA-IMP test showed 20 out of 40 (50%) imipenem-resistant strains were MBL positive. Furthermore, by molecular studies, 50% of imipenem-resistant strains were detected to have bla_VIM-1, 56.6% bla_VIM-2, 6.6% bla_IMP-1. In addition, two other genes (bla_IMP-2 and bla_SPM-1) were not detected in imipenem-resistant P. aeruginosa strains. This study showed resistance to imipenem like other countries is increasing, and there are P. aeruginosa strains carrying MBL genes in Markazi province.

Key words: β-lactamase, bla_IMP, bla_SPM, bla_VIM, imipenem resistance, metallo-β-lactamase genes, Pseudomonas aeruginosa.