Carbapenem Resistance in Non-Fermenters: An Overview

Abstract

This study was conducted with interest in increasing carbapenem resistance in non-fermenters: an important causative agent of nosocomial infection and to standardize the methods for interpretation of their resistance. The aim of this study is to perform disk diffusion testing and minimal inhibitory concentration technique for the identification of carbapenem resistance for imipenem and meropenem. The isolates found resistant to carbapenems were confirmed with the modified Hodge test. The genes responsible for carbapenem resistance were identified by both phenotypic and genotypic methods. Out of 240 non-fermenters isolated 20% showed resistance to carbapenem by disk diffusion. Only 7% showed resistance by the micro broth dilution technique of minimum inhibitory concentration. 3% were panning drug-resistant. Out of 16 carbapenem-resistant isolates, 5 were found to have KPC (Klebsiella pneumonia carbapenem) genes, 9 had MBL (Metallo beta-lactamase) genes and 2 had KPC+MBL genes and none were found to have Amp C and OXA-48 genes phenotypically. Genotypically all the KPC strains had KPC genes and out of 9 MBL strains, 6 had VIM and the remaining 3 strains were negative for both IMP and VIM gene. In conclusion, the interpretation of susceptibility for carbapenems should not be made only with disk diffusion testing. Always check for Minimal inhibitory concentration methods and determination of genes responsible for carbapenem resistance, a double-disc synergy test goes in hand with genotypic detection.