Imipenem-resistant Pseudomonas aeruginosa strains carry metallo-beta-lactamase gene bla(VIM) in a level I Iranian burn hospital

Abstract

Introduction: In this study, we aimed to determine the distribution of bla(VIM) and bla(IMP) transferable genes in Pseudomonas aeruginosa isolates from infected burn wounds in an Iranian level I burn care center. These genes confer imipenem resistance and increase the mortality rate of burn patients.

Methods: P. aeruginosa isolates from burn patients were tested for antibiotic susceptibility with Kirby-Bauer disk diffusion method and for production of metallo-beta-lactamase (MBL) by EDTA disk method. DNA was purified from isolates with positive MBL results and underwent PCR for detection of bla(VIM) and bla(IMP) genes.

Results: MBL was produced by 23 imipenem-resistant isolates and bla(VIM) gene was detected in all of these isolates. None of the isolates carried bla(IMP) gene. Mortality rate of infection with MBL-producing Pseudomonas strains was 82.6% in this hospital while the mortality rate for non-MBL-producing Pseudomonas was 22.7%.

Conclusion: We found that all MBL-producing isolates in this hospital carry bla(VIM) gene. This result is similar to the previous Iranian study and emphasizes the importance of VIM family of MBLs in Iran. Timely identification of these strains and strict isolation methods can prevent spread of this transferable gene to other Gram-negative bacteria and prevent the subsequent outbreak of high mortality.