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Objectives This study examined Klebsiella pneumoniae clinical isolates and their blaKPC plasmids to determine potential relatedness of the isolates and their plasmids harbouring carbapenem resistance mechanisms. Methods K. pneumoniae carbapenemase (KPC)-producing K. pneumoniae from New York City (NYC) (n = 19) and Toronto (n = 2) were typed by PFGE and multilocus sequence typing (MLST). blaKPC-harbouring plasmids were transformed into Escherichia coli DH10BTM, restricted using EcoRI and analysed for bla content and replicon (rep) type. Susceptibility profiles for clinical and transformed strains were determined by automated microbroth dilution using CLSI breakpoints. Outer membrane protein (OMP) genes were analysed by sequencing of ompk35 and ompk36. Results PFGE analysis identified 17 related strains (≥80% similarity; 11 KPC-2, 6 KPC-3) where ST258 was the dominant clonal type. All clinical isolates contained both blaSHV and blaTEM-1 and, with the exception of one isolate, were multidrug resistant (MDR). Transformed KPC plasmids (n = 21) carried TEM-1 (n = 18) and were MDR (n = 5). Three plasmid clusters, repFIIA (n = 10), repR (n = 3) and an unknown type (n = 3), were observed. repFllA plasmids were observed from both NYC and Toronto strains. OMP gene analysis revealed premature stop codons in ompk35 and numerous deletions and insertions in ompk36. Conclusions The dissemination of blaKPC is due both to carriage of similar KPC-harbouring plasmids within genetically distinct K. pneumoniae and to clonal spread of K. pneumoniae with unrelated KPC plasmids. [ABSTRACT FROM PUBLISHER]