English

Abstract

BACKGROUND: Carbapenemases are emerging resistance determinants in Gramnegative pathogens, including Pseudomonas aeruginosa, Acinetobacter spp and Enterobacteriaceae. Acquired carbapenem resistance is largely attributed to the production of carbapenem‐hydrolysing enzymes called carbapenemases which include metallo‐beta‐lactamases (MBLs) or Klebsiella pneumoniae carbapenemases (KPCs). Detection of these enzymes has become a diagnostic challenge for clinical microbiologists. The present study was undertaken to assess the incidence of carbapenemases including KPCs and MBLs in urinary isolates of Enterobacteriaceae. MATERIALS AND METHODS: A total of 66 consecutive, non-repeat carbapenems resistant (by disk diffusion) clinical isolates of Enterobacteriaceae obtained over a period of one year (January-December, 2011) were subjected to modified Hodge test (MHT) for the detection of carbapenemases, combined disk test using phenylboronic acid(PBA) for KPC, EDTA double disk synergy test, combined disk test using EDTA, MBL Etest for MBL, and disk enhancement test with both PBA and EDTA for detecting coproduction of KPC and MBL. RESULTS: Of the total 66 resistant clinical isolates, MHT identified 61 (92.42%) isolates as carbapenemase producers, metallo-beta-lactamases (MBLs) activity was detected in 39(59.09%) isolates, KPC in 9(13.63%) and co-existent of both KPC and MBL in 3(4.54%) isolates. CONCLUSIONS: The study demonstrates the presence of carbapenemases including KPCs and MBLs in Enterobacteriaceae in our hospital. The combined disk test and MBL Etest show equal efficacy for MBL detection, but given the cost-constraints, combined disk test can be used as a convenient detection method in the clinical microbiology laboratory. Boronic acid disk test is easy to perform, interpret and reliable method in detecting KPCs.