Molecular detection of metallo‑β‑lactamase gene blaVIM‑1 in imipenem‑resistant Pseudomonas aeruginosa strains isolated from hospitalized patients in the hospitals of Isfahan

Pseudomonas aeruginosa is an opportunistic human pathogen that causes serious problems, especially in people, who have immunodeficiency. In recent times, metallo‑β‑lactamase (MBLs) resistance in this bacterium has led to some difficulties in treating bacterial infections. The metallo‑beta‑lactamase family of genes, including blaVIM‑1, is being reported with increasing frequency worldwide. The aim of this study is the detection of the metallo‑β‑lactamase gene blaVIM‑1 in imipenem‑resistant P. aeruginosa (IRPA) strains isolated from hospitalized patients.

In this study, 106 P. aeruginosa samples were isolated from various nosocomial infections. The isolates were identified, tested for susceptibility to various antimicrobial agents by the Kirby‑Bauer disk diffusion method, and all the imipenem‑resistant isolates were screened for the presence of MBLs by using the combined disk (IMP‑EDTA). The minimal inhibitory concentration (MIC) of imipenem was determined by E‑test on the Mueller‑Hinton agar. To detect the blaVIM‑1 gene, the isolates were subjected to a polymerase chain reaction (PCR).

Of all the P. aeruginosa isolates, 62 (58.5%) were found to be imipenem‑resistant P. aeruginosa (MIC ≥32 μg/ml). Twenty‑six (42%) of the imipenem‑resistant isolates were MBL positive. None of these isolates carried the blaVIM‑1 gene using the PCR assay.

The results demonstrated the serious therapeutic threat of the MBL‑producing P. aeruginosa populations. The rate of imipenem resistance due to MBL was increased dramatically. Early detection and infection‑control practices are the best antimicrobial strategies for this organism. None of MBL‑producing isolates in this study carry the blaVIM‑1 gene; therefore, another gene in the MBL family should be investigated.