Molecular characterization of Klebsiella pneumoniae Carbapenemase (KPC)-producing Enterobacteriaceae in Ontario, Canada, 2008-2011

Abstract

Due to the lack of detailed reports of Klebsiella pneumoniae carbapenemase (KPC)-producing enterobacteria in Ontario, Canada, we perform a molecular characterization of KPC-producing Enterobacteriaceae submitted to the provincial reference laboratory from 2008 to 2011. Susceptibility profiles were accessed by E-test. Molecular types of isolates were determined by pulse-field gel electrophoresis (PFGE) and multilocus sequence typing. Screening of β-lactamase genes was performed by multiplex PCR and alleles were identified by DNA sequencing. The genetic platform of blaKPC gene was analyzed by PCR. Plasmid replicons were typed using PCR-based typing approach. KPC-plasmids were also evaluated by S1 nuclease-PFGE and Southern blot. Thirty unique clinical isolates (26 Klebsiella pneumoniae, 2 Enterobacter cloacae, 1 Citrobacter freundii and 1 Raoultella ornithinolytica) were identified as blaKPC positive: 4 in 2008, 3 in 2009, 10 in 2010 and 13 in 2011. The majority exhibited resistance to carbapenems, cephalosporins and fluoroquinolones and two isolates were also resistant to colistin. The isolates harbored blaKPC-2 (n=23) or blaKPC-3 (n=7). blaTEM-1 (n=27) was commonly detected and occasionally blaOXA-1 (n=3) and blaCTX-M-15 (n=1). As expected, all K. pneumoniae isolates carried blaSHV-11. blaKPC genes were identified on Tn4401a (n=20) or b (n=10) isoforms, on plasmids of different sizes belonging to the incompatibility groups IncFIIA (n=19), IncN (n=3), IncI2 (n=3), IncFrep (n=2) and IncA/C (n=1). The occurrence of KPC β-lactamase in Ontario was mainly associated with the spread of the K. pneumoniae clone ST258.