Increasing prevalence and dissemination of NDM-1 metallo- -lactamase in India: data from the SMART study (2009)

Abstract

To investigate the β-lactamase background of ertapenem non-susceptible isolates for the presence of the most commonly detected carbapenemase genes, bla_KPC, bla_OXA-48 and bla_VIM, and the newly described bla_NDM-1. Two hundred and thirty-five ertapenem-non-susceptible (MIC ≥0.5 mg/L) isolates of Enterobacteriaceae from the worldwide Study for Monitoring Antimicrobial Resistance Trends (SMART) 2009 programme were screened using a multiplex PCR for the presence of bla_KPC, bla_OXA-48, bla_VIM and bla_NDM-1 genes. Extended-spectrum β-lactamase (ESBL) and AmpC genes (bla_ESBL and bla_AmpC) were identified using the Check-MDR CT101 microarray. DNA sequencing was performed to identify the bla_ESBL, bla_KPC and bla_NDM-1 genes. Molecular typing was also performed to genetically characterize these isolates. Sixty-six isolates (28%) had a carbapenemase gene, with bla_NDM-1 identified in 33 isolates including 2 isolates carrying both bla_NDM-1 and bla_OXA-48; other carbapenemase genes found included bla_KPC (n = 23), bla_VIM (n = 7) and bla_OXA-48 (n = 3). All bla_NDM-1-carrying isolates were from patients in India and comprised five different species. With the exception of one isolate carrying only bla_NDM-1, all bla_NDM-1 carbapenemase-possessing isolates carried additional β-lactamases in various combinations: bla_ESBL and bla_AmpC (n = 18); bla_ESBL (n = 10); bla_ESBL, bla_AmpC and bla_OXA-48 (n = 2); and bla_AmpC (n = 2). Except for bla_OXA-48-carrying isolates, novel multilocus sequence types or enterobacterial repetitive intergenic consensus PCR patterns were observed along with clonal dissemination within and among sites. A range of carbapenemase genes, associated with diverse ESBLs and/or AmpC backgrounds, were found among Enterobacteriaceae isolated during the study. Many of these ertapenem non-susceptible strains were clonally related and carried various combinations of β-lactamases.