Occurrence of blaNDM-1 & absence of blaKPC genes encoding carbapenem resistance in uropathogens from a tertiary care centre from north India

Background & objectives: Carbapenem resistance mediated by carbapenemases is increasingly being reported worldwide. This study was conducted to know the occurrence of important carbapenem resistance encoding genes in gram-negative bacilli (GNB) causing complicated urinary tract infection (CUTI), and to look at the genetic diversity of these isolates. Methods: The study was carried out on 166 consecutive carbapenem resistant uropathogens (CRU) isolated from cases with CUTI during 2008 and 2012. Carbapenemase production was characterized phenotypically and polymerase chain reaction was used to detect bla(VIM), bla(IMP), bla(KPC), and bla(NDM-1). BOX-PCR was done on 80 randomly selected isolates for molecular typing. Results: The bla(VIM) gene was present in 34 (43.6%), bla(IMP) in five (6.4%) and none of the isolates from 2008 had bla(NDM-1) or bla(KPC) genes. Among the isolates from 2012, bla(NDM-1) gene was present in 47 (53.4%), bla(VIM) in 19 (24.4%), bla(IMP) in one (1.1%) and none had bla(KPC). There were nine isolates during the two years which had multiple genes encoding carbapenemases; while 66 did not have any of the genes tested. Of the 80 isolates subjected to BOX-PCR, 58 could be used for analysis and showed, presence of multiple clusters of carbapenem resistant isolates and absence of a single dominant clone. Interpretation & conclusions: The bla(NDM-1) gene was absent in our isolates obtained during 2008 but was present amongst Enterobacteriaceae isolated in 2012. The bla(KPC) gene was also not found. Nine isolates obtained during the two years had multiple genes encoding carbapenemases confirming the previous reports of emergence of GNB containing genes encoding multiple carbapenemases. Typing using BOXPCR indicated that this emergence was not because of clonal expansion of a single strain, and multiple strains were circulating at a single point of time.