Carbapenemase Producing Bugs : A Threat to Antimicrobial Therapy

Abstract

CONTEXT: Carbapenemases are a group of β-lactamases capable of conferring resistance to carbapenems. Carbapenemase producing gram negative bacilli are becoming increasingly prevalent not only in nosocomial infections but in community acquired isolates also posing a threat to antimicrobial therapy of life threatening infections. AIMS & OBJECTIVES: This study was done to identify carbapenemase producing organisms among multidrug resistant clinical isolates and to detect MBL producers among the carbapenemase producing isolates. MATERIALS & METHODS: Gram negative organisms isolated from clinical samples in November-December 2014 were included. The antibiotic susceptibility of isolates was determined by Kirby Bauer method. Multidrug resistant isolates showing reduced suceptibility or resistance to carbapenems were further tested for carbapenemase production by Modified Hodge test (MHT) and MHT positive isolates were further tested for MBL production by combined disc synergy test (CDST). RESULTS: A total of 32 isolates out of 62 carbapenem resistant MDR isolates were positive for carbapenemase production by MHT. Most common isolated carbapenemase producing organisms are Klebsiella species, Escherichia coli, Pseudomonas species and Acinetobacter species. Out of the 32 MHT positive isolates, 4 were positive for MBL production by CDST. MBL producers were 2 Klebsiella isolates, 1 Pseudomonas and 1 Acinetobacter isolate. CONCLUSION: Evaluation of effective antibiotic options and rigorous infection control measures are needed for controlling spread of carbapenemase producing multidrug resistant organisms, especially in hospital setting.