Phenotypic detection and molecular characterization of carbapenem-resistant Enterobacteriaceae at a tertiary care center

Background: Carbapenem-resistant Enterobacteriaceae (CRE) is of utmost clinical importance because they challenge the armamentarium of the treating clinicians, hampering current treatment strategies. Aim: The aim of the study is to detect carbapenemase-producing Enterobacteriaceae by phenotypic and molecular methods. Materials and Methods: Nonrepetitive isolates of Enterobacteriaceae were identified by conventional phenotypic methods from various clinical samples. All these isolates were screened for carbapenem resistance by meropenem (10 mu g) or ertapenem (10 mu g) disc. All the isolates which were found to be carbapenem-resistant by screening test were subjected to phenotypic confirmatory test in the form of modified Hodge test (MHT). These isolates were then subjected to polymerase chain reaction for the detection of various carbapenemase-producing genes, namely New Delhi metallo-beta-lactamase 1 (NDM), verona integron-encoded metallo-beta-lactamase (VIM), imipenem-resistant Pseudomonas (IMP), KPC, and OXA-48. Results: Out of 1254 isolates of Enterobacteriaceae, 230 isolates (18.3%) were found to be positive for carbapenemase production by screening test. A total of 150 out of 230 isolates (65.2%) tested positive for carbapenemase production by MHT. Out of these 150 phenotypically confirmed carbapenemase-producing isolates, blaNDM gene was found in 85, blaVIM in 32, and blaIMP in 22 isolates. blaOXA-48 and blaKPC genes were not found in any isolate. Moreover, there were 19 isolates, in which no gene was detected. Conclusion: The prevalence of phenotypically confirmed carbapenemase resistance among Enterobacteriaceae is 11.96% (150/1254). Genes responsible for carbapenemase production are widely prevalent in Enterobacteriaceae Routine detection will help in the management of these broadly-resistant pathogens and implementation of appropriate infection control measures, thus limiting their spread.