There is little information about carbapenemase-producing (CP) Klebsiella oxytoca, an important nosocomial pathogen. We characterized CP K. oxytoca isolates collected from different Spanish hospitals between January 2016 and October 2017. During the study period, 139 nonduplicate CP K. oxytoca isolates were identified; of these, 80 were studied in detail. Carbapenemase and extended-spectrum β-lactamase genes were identified by PCR and sequencing. Genetic relatedness was studied by pulsed-field gel electrophoresis (PFGE). Whole-genome sequencing (WGS), carried out on 12 representative isolates, was used to identify the resistome, to elucidate the phylogeny, and to determine the plasmids harboring carbapenemase genes. Forty-eight (60%) isolates produced VIM-1, 30 (37.5%) produced OXA-48, 3 (3.7%) produced KPC-2, 2 (2.5%) produced KPC-3, and 1 (1.2%) produced NDM-1; 4 isolates coproduced two carbapenemases. By PFGE, 69 patterns were obtained from the 80 CP K. oxytoca isolates, and four well-defined clusters were detected: cluster 1 consisted of 11 OXA-48-producing isolates, and the other three clusters included VIM-1-producing isolates (5, 3, and 3 isolates, respectively). In the 12 sequenced isolates, the average number of acquired resistance genes was significantly higher in VIM-1-producing isolates (10.8) than in OXA-48-producing isolates (2.3). All 12 isolates had chromosomally encoded genes of the blaOXY-2 genotype, and by multilocus sequence typing, most belonged to sequence type 2 (ST2). Carbapenemase genes were carried by IncL, IncHI2, IncFII, IncN, IncC, and IncP6 plasmid types. The emergence of CP K. oxytoca was principally due to the spread of VIM-1- and OXA-48-producing isolates in which VIM-1- and OXA-48 were carried by IncL, IncHI2, IncFII, and IncN plasmids. ST2 and the genotype blaOXY-2 predominated among the 12 sequenced isolates.
Keywords: Klebsiella oxytoca; carbapenemases; cgMLST; plasmids; whole-genome sequencing.
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