Prevalence and characterization of carbapenemase producing isolates of Enterobacteriaceae obtained from clinical and environmental samples: Efflux pump inhibitor study

The present study was undertaken to screen for carbapenem resistance and the ability of efflux pump inhibitors to inhibit this resistance in enterobacteriaceae strains isolated from clinical specimens from patients attending Jawaharlal Institute of Post Graduate Medical Education and Research (JIPMER) hospital and water samples in and around Puducherry. A total of 425 carbapenem resistant isolates from clinical samples were studied by both phenotypic and genotypic methods. Two hundred and forty eight (248) strains were positive for metallo beta lactamase in the double disk synergy test (DDST) and 264 strains were positive for modified Hodge test (MHT). Multiplex PCR assays revealed that 262 of the 425 strains harboured blaNDM-1 gene. Efflux pump inhibitory activity of Phenylalanine arginine beta-naphthylamide (PAβN) was detected for these strains. This study demonstrates that, 30 strains out of 163 blaNDM-1 negative strains were found to exhibit efflux pump activity. This study brings out the fact that such carbapenem resistant strains are limited only to clinical samples and not found in water samples in and around Puducherry.