Molecular Analysis of blaKPC-2-Harboring Plasmids: Tn 4401a Interplasmid Transposition and Tn 4401a-Carrying ColRNAI Plasmid Mobilization from Klebsiella pneumoniae to Citrobacter europaeus and Morganella morganii in a Single Patient

Abstract

The spread of Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacterales is a public health concern. KPC-encoding bla_KPC is predominantly spread by strains of a particular phylogenetic lineage, clonal group 258, but can also be spread by horizontal transfer of bla_KPC-carrying plasmids. Here, we report the transfer of a bla_KPC-2-harboring plasmid via mobilization from K. pneumoniae to Citrobacter freundii complex and Morganella morganii strains in a single patient. We performed draft whole-genome sequencing to analyze 20 carbapenemase-producing Enterobacterales strains (15 of K. pneumoniae, two of C. freundii complex, and three of M. morganii) and all K. pneumoniae strains using MiSeq and/or MinION isolated from a patient who was hospitalized in New York and Montreal before returning to Japan. All strains harbored bla_KPC-2-containing Tn4401a. The 15 K. pneumoniae strains each belonged to sequence type 258 and harbored a Tn4401a-carrying multireplicon-type plasmid, IncN and IncR (IncN+R). Three of these K. pneumoniae strains also possessed a Tn4401a-carrying ColRNAI plasmid, suggesting that Tn4401a underwent interplasmid transposition. Of these three ColRNAI plasmids, two and one were identical to plasmids harbored by two Citrobacter europaeus and three M. morganii strains, respectively. The Tn4401a-carrying ColRNAI plasmids were each 23,753 bp long and incapable of conjugal transfer via their own genes alone, but they mobilized during the conjugal transfer of Tn4401a-carrying IncN+R plasmids in K. pneumoniae. Interplasmid transposition of Tn4401a from an IncN+R plasmid to a ColRNAI plasmid in K. pneumoniae and mobilization of Tn4401a-carrying ColRNAI plasmids contributed to the acquisition of bla_KPC-2 in C. europaeus and M. morganii. IMPORTANCE Plasmid transfer plays an important role in the interspecies spread of carbapenemase genes, including the Klebsiella pneumoniae carbapenemase (KPC)-coding gene, bla_KPC. We conducted whole-genome sequencing (WGS) analysis and transmission experiments to analyze bla_KPC-2-carrying mobile genetic elements (MGEs) between the bla_KPC-2-harboring K. pneumoniae, Citrobacter europaeus, and Morganella morganii strains isolated from a single patient. bla_KPC-2 was contained within an MGE, Tn4401a. WGS of bla_KPC-2-carrying K. pneumoniae, C. europaeus, and M. morganii strains isolated from one patient revealed that Tn4401a-carrying ColRNAI plasmids were generated by plasmid-to-plasmid transfer of Tn4401a from a multireplicon-type IncN and IncR (IncN+R) plasmid in K. pneumoniae strains. Tn4401a-carrying ColRNAI plasmids were incapable of conjugal transfer in C. europaeus and M. morganii but mobilized from K. pneumoniae to a recipient Escherichia coli strain during the conjugal transfer of Tn4401a-carrying IncN+R plasmid. Therefore, Tn4401a-carrying ColRNAI plasmids contributed to the acquisition of bla_KPC-2 in C. europaeus and M. morganii.

Keywords: KPC-producing organisms; Tn4401a; WGS; blaKPC-2; plasmid.

FIG 1

Phylogenetic tree of bla_KPC-2-positive Klebsiella pneumoniae strains. Phylogenetic tree of the 15 bla_KPC-2-positive K. pneumoniae strains and information on their harbored plasmids. The phylogenetic tree was constructed using a maximum-likelihood phylogenetic analysis based on single nucleotide polymorphisms (SNPs) in the core genome and excluding homologous recombination sequences. We used the bootstrap 1,000 times and listed the bootstrap values on the branch. The core-genome region comprised 95.1% (5,130,070/5,394,056 bp) of the genome of the reference strain, K. pneumoniae KPNIH1 ST258 (GenBank accession number NZ_CP008827.1). The scale distance corresponds to the number of SNPs per the core genome, excluding the homologous recombination sequence.