Antimicrobial Resistance Caused by KPC-2 Encoded by Promiscuous Plasmids of the Klebsiella pneumoniae ST307 Strain.

Background: A lineage of Klebsiella pneumoniae that produces carbapenemase-2 (KPC-2), sequence type (ST) 307, emerged in 2017. We analyzed the complete sequences of plasmids from KPC-2-producing K. pneumoniae (KPC-Kp) ST307, investigated the antimicrobial resistance conferred by this strain, and confirmed the horizontal interspecies transmission of KPC-carbapenemase-producing Enterobacteriaceae (CPE) characteristics among Enterobacteriaceae.

Methods: We performed antimicrobial susceptibility testing, PCR analysis, multilocus sequence typing, curing tests, and whole-genome sequencing to characterize plasmid-derived KPC-2-producing Enterobacteriaceae clinical isolates.

Results: Sequence analysis of KPC-Kp strain ST307 revealed novel plasmid-located virulence factors, including a gene cluster for glycogen synthesis. Three Enterobacteriaceae strains were identified in one patient: K. pneumoniae (CPKp1825), Klebsiella aerogenes (CPEa1826), and Escherichia coli (CPEc1827). The bla KPC-2 gene from K. pneumoniae ST307 was horizontally transmitted between these strains. The plasmids could be transferred through conjugation, because all three strains of bacteria contained the type IV secretion system, pilus genes, and tra genes for conjugal transfer. The bla KPC-2 gene was located on a truncated Tn4401 transposon. Plasmids containing the bla KPC-2 gene could not be artificially removed; thus, the three strains could not be cured.

Conclusions: The ease of horizontal transfer of KPC-Kp ST307 carbapenem resistance has serious public health and epidemiological implications. This study provides a better understanding of the genetic characteristics that can contribute to the growth and spread of KPC-Kp ST307, and their association with antimicrobial resistance genes.