Co-existence of blaKPC-2 and blaVIM-2 in highly carbapenem-resistant Pseudomonas aeruginosa isolated in the ICU of a public hospital
In this study, highly carbapenem-resistant Pseudomonas aeruginosa (h-CRPA) 18102011 [the minimum inhibitory concentration (MIC) value of carbapenem antimicrobial imipenem (IP) for h-CRPA is 4,096 g/mL] was isolated from the bile of an intensive care unit (ICU) burn patient in China, and genomic sequencing revealed a complete genome. The genomes molecular characteristics were analyzed to assess the genetic environment of blaKPC-2 and blaVIM-2. Average nucleotide identity (ANI) comparisons were used for precise species-level identification, while serotyping, multi-locus sequence typing, and the identification of acquired resistance genes, and virulence genes were also carried out. The h-CRPA 18102011 strain carrying blaKPC-2 and blaVIM-2 was identified as strain ST2374 and the O4 serotype. Virulence genes (plcH, exoST) and resistance genes (aph(3)-IIb, aac(6)-Ib-cr, ant(2)-Ia, blaOXA-396, blaPAO, blaKPC-2, blaVIM-2, blaPER-1, sul1, catB7, qnrVC6, fosA) were both identified in the genome. In addition, the IncpRBL16 type mega-plasmid pP2011-1 carrying blaVIM-2 and the IncP6 type plasmid pP2011-2 carrying blaKPC-2 were identified in the strain. The genetic environment of blaVIM-2 and blaKPC-2 was specifically evaluated to assess their origins. blaVIM-2 was located in the region of In2075 (a novel type 1 integron) that was inserted into plasmid pP2011-1, this plasmid contained 3 novel recombination sites, as well as the typical recombination site 2 (umuC) observed for IncpRBL16 type plasmids. However, the core module Tn3-ISKpn27-blaKPC-{Delta}ISKpn6 was identified as the blaKPC-2 platform in plasmid pP2011-2. Conjugation experiments revealed that the plasmids pP2011-1 and pP2011-2 of the h-CRPA 18102011 strain could be transferred into Escherichia coli with a conjugation transfer efficiency of 10-6. The E. coli transconjugant carried blaKPC-2 and blaVIM-2 from the donor and the MIC value of IP to the E. coli transconjugant was 4,096 g/mL, which was the same as observed for the donor. Overall, this study revealed the molecular characteristics of a VIM-2 and KPC-2-co-producing strain that was typed as O4 and ST2374. The continuous monitoring of bacteria, such as the strain investigated here, that co-harbor different types of carbapenemase genes is critical for preventing the spread of these genes.