blaIMP and blaVIM mediated carbapenem resistance in pseudomonas and acinetobacter species in India

Abstract

Introduction: The emergence and rapid spread of blaIMP and blaVIMmetallo-beta-lactamase (MBL) producing Gram-negative bacteria causing nosocomial infections are of concern worldwide due to limited treatment options. Methodology: A total of 179 nonreplicate, consecutive, carbapenem resistant Pseudomonas aeruginosa (61), Acinetobacter baumannii (116), Acinetobacter lwoffii (1) and Pseudomonas stutzeri (1) isolated from patients hospitalized for 48 hours or more were included in the study. The minimum inhibitory concentrations (MIC) to imipenem and meropenem were determined and interpreted according to Clinical Laboratory Standards Institute guidelines. The Modified Hodge Test (MHT) and inhibitor potentiated disk diffusion tests with ethylenediaminetetraacetic acid (EDTA) were used for screening of carbapenamases and MBL production respectively. Polymerase chain reaction (PCR) was performed for the detection of MBL (blaVIM and blaIMP) genes. Gene sequencing was performed for representative isolates. Results: MHT was positive in 94.4% (n = 169). MBL screening with EDTA was positive in 80.4% (n = 144). MBL genes blaVIM and blaIMP were detected in 92 (51.4%) isolates. BlaVIM alone was detected in 89 isolates while two isolates had blaIMP alone. One isolate had both blaVIM and blaIMP. Among the P. aeruginosa, 36 carried the MBL gene. In A. baumannii, 54 carried the MBL gene. BlaVIM was found in P. stutzeri and A. lwoffii isolates. Conclusion: Carbapenem resistance in P. aeruginosa and A. baumannii is chiefly mediated by MBL production. The common MBL gene is the blaVIM. © 2012 Amudhan et al.