In vivo horizontal dissemination of the blaKPC-2 gene carried on diverse genetic platforms among clinical isolates of Enterobacteriaceae

This study investigated the molecular characteristics of six blaKPC-positive Enterobacteriaceae recovered from three patients in Argentina. Antimicrobial susceptibility testing was performed following Clinical and Laboratory Standards Institute (CLSI) 2014 recommendations. Molecular characterisation of the isolates was performed by biparental conjugation, PCR, sequencing, S1 nuclease restriction, and Southern blot hybridisation with a blaKPC probe using standard protocols and conditions. The isolates studied were as follows. Case 1: Escherichia coli (ECO-P1) and Klebsiella pneumoniae (KPN-P1) isolated from a rectal swab harboured blaKPC-2 in transposon Tn4401a on non-typeable and non-conjugative plasmids. Case 2: Enterobacter cloacae (ECL-P2) and K. pneumoniae (KPN-P2) were isolated from two blood cultures. blaKPC-2 was found in a novel genetic variant of ISKpn8-blaKPC-2-ISKpn6-like on conjugative plasmids of IncL/M type. Case 3, Citrobacter freundii (CFR-P3) and Klebsiella oxytoca (KOX-P3) were isolated from skin and skin-structure infection. The blaKPC gene was detected on ISKpn8-ΔblaTEM-blaKPC-2-ISKpn6-like located on an IncA/C conjugative plasmid. CFR-P3 and KOX-P3 harboured blaPER-2 in addition to the blaKPC gene. In conclusion, we document the horizontal dissemination of blaKPC-2 from diverse Enterobacteriaceae clinical isolates with different genetic backgrounds. This is the first report of E. coli harbouring blaKPC associated with Tn4401a in Argentina.