Detection and Genetic Characterization of Metallo-β- Lactamase IMP-1 and VIM-2 in Pseudomonas aeruginosa Strains From Different Hospitals in Kermanshah, Iran

Background: Pseudomonas aeruginosais a frequent nosocomial pathogen that causes severe diseases in many settings. Carbapenems, including meropenem and imipenem, are effective antibiotics against this organism. However, the use of carbapenems has been hampered by the emergence of strains resistant to carbapenemsvia different mechanisms such as the production of metallo-β-lactamases (MBLs), which hydrolyze all carbapenems. Several kinds of MBLs have been reported, among them VIM and IMP types being the most clinically significant carbapenemases. Objectives: We aimed to determine the distribution of blaVIM-2 and blaIMP-1 transferable genes encoding MBLs in P. aeruginosa isolated from three academic hospitals in Kermanshah. Patients and Methods: From 22nd June to 22nd September 2012, 225 isolates of P. aeruginosa were collected. These isolates were tested for antibiotic susceptibility with the Kirby-Bauer disk-diffusion method, and the MBLs were assessed using the imipenem-EDTA double-disk synergy test. The isolates were investigated for blaVIM-2 and blaIMP-1 genes using polymerase chain reaction. Results: Among the 225 isolates, 33.7% (76/225) and 18.1% (41/225) were resistant to imipenem and meropenem, respectively. Of the 76 imipenem-resistant P. aeruginosa strains, 45 (59.2%) were positive for MBLs, 34 (75%) strains carried the blaIMP-1 gene, and 1 (2.2%) strain carried the blaVIM-2 gene. Conclusions: Our results showed that there was a high frequency of IMP-1 positive P. aeruginosa in the different wards of the hospitals.