European Journal of Biomedical and Pharmaceutical Sciences

EVALUATION OF VARIOUS PHENOTYPIC METHODS FOR DETECTION OF CARBAPENEMASE PRODUCTION IN CARBAPENEM RESISTANT GRAM NEGATIVE BACTERIA.

Sriparna Chakravorty*, Soma Sarkar, Manideepa SenGupta, Anita Nandi (Mitra), Sonia Jain, Arunansu Talukdar

ABSTRACT

Introduction : A carbapenemase is a β-lactamase that hydrolyses carbapenems. This study was undertaken to compare the various phenotypic methods to detect carbapenemase production in carbapenem resistant Gram negative bacteria obtained from clinical samples in a tertiary care hospital, Kolkata. Aim - Evaluation of various phenotypic methods for detection of carbapenemase production. Materials and methods – Those Gram negative bacilli that were found to be carbapenem resistant or intermediate sensitive were tested by automated system .All the Gram negative bacilli with reduced susceptibility to carbapenems were further subjected to phenotypic tests for detection of carbapenemase. The results of the phenotypic tests were compared with that of an automated system. Results: 1404 Gram negative bacilli were isolated, out of which 148(10.54%) were found to have reduced susceptibility. E.coli was isolated in 37.16% cases followed by Klebsiella spp 26.35%, Acinetobacter spp.22.3%, Pseudomonas spp.7.43%, Citrobacter spp.3.38% and Enterobacter spp. 3.38%. 35(23.6%) were found to produce carbapenemase on testing with an automated system. Out of the total 35 carbapenemase producing GNB,32 were correctly detected by double disc synergy test,29 were correctly detected by modified Hodge test , 25 were correctly detected by E – test and 19 were correctly detected by combined disc test. The sensitivity was found to be 91.42% for double disc synergy test (DDST),82.86% for modified Hodge test (MHT), 71.43% for E – test and 54.29% for combined disc test(CDT). Conclusion - Our study showed that DDST was the most effective test to detect carbapenemase, particularly MBL production, followed by MHT.

Keywords: Metallo – ? - lactamase, clinical isolates, ?-lactams.