Carbapenamase Detection: An Imperative Call

Aim This study intended to determine carbapenamase production among Multi drug resistant gram negative bacteria by Disk Diffusion method, Vitek 2 and Modified Hodge and to determine MBL positive isolates by combined disk test and Double Disk Synergy Test. Methodology In the present study, 550 gram negative isolates were isolated from different clinical samples and identified by Vitek 2 ( BioMrieux). Antimicrobial susceptibility testing was performed by modified Kirby Bauer disk diffusion method using various antibiotics. MIC concentration was further determined by Vitek 2. Carbapenamase production was identified by Modified Hodge Test and MBL positive isolates among carbapenem resistant isolates were determined by Combined Disk Method and Double Disk Synergy test. Results Out of 550 isolates, 163 (29.64 %) exhibited resistance to carbapenem by disc diffusion and Vitek 2. Maximum number of carbapenem resistant isolate was obtained from urine (n=74), followed by Endotracheal secretion (n=27) and sputum (n=27). MHT for carbapenamase production was positive in 160 (98.2 %) of the isolates. Carbapenamase production by MHT was highest with Acinetobacter spp. , n=15 (100 %), Klebsiella spp. , n=73 (98.64 %), followed by E. coli spp. with n = 33 ( 97.1 %). MBL isolates, determined by combined disk and double disk synergy test were positive in 62 ( 38 %) of the isolates and three isolates were negative for both MHT and MBL screening. Conclusion Use of MHT, combined disc test and double disk synergy test with EDTA as a screening method can increase the sensitivity of detection of carbapenamase and can aid timely intervention to initiate infection control practices and thereby improve patient outcome.