Molecular characterization of blaKHM-1 encoding plasmid in an Enterobacter hormaechei subsp. hoffmannii isolate from blood culture

PLoS One. 2020 Jan 13;15(1):e0227605. doi: 10.1371/journal.pone.0227605. eCollection 2020.

Abstract

KHM-1 was first reported in 1997 in Japan as a novel metallo-β-lactamase mediated by Citrobacter freundii carrying pKHM-1 plasmid. There have been few reports in the clinical field since then. A blaKHM-1-positive Enterobacter hormaechei subsp. hoffmannii in E. cloacae complex, isolate OIPH-N069 was isolated from an inpatient blood culture in 2016. The isolate was characterized by whole-genome sequencing, comparative analysis of the blaKHM-1 encoding plasmid, antimicrobial susceptibility tests, and bacterial conjugation. OIPH-N069 was classified into ST78 of E. cloacae complex, and was multidrug resistant because of the presence of antimicrobial resistance genes in addition to blaKHM-1 on its chromosome and plasmids. blaKHM-1 was located on 136,816 bp of the IncA/C2 plasmid pN069-1, which could be transferred to different bacterial species. The backbone structure, genetic arrangement of the class 1 integron cassette, and the blaKHM-1 gene located downstream of the IncA/C2 antibiotic resistance island, ARI-A, in pN069-1 and pKHM-1 were identical. Horizontal gene transfer of the blaCTX-M-2-ISEcp1 resistance gene module only occurred with pN069-1. The study findings indicate not only the structural conservation of blaKHM-1 encoding plasmids over time and across species, but also the risk of the spread of blaKHM-1 encoding plasmids to other bacterial species and the accumulation of additional resistance genes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / therapeutic use
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Blood / microbiology
  • Blood Culture
  • Conserved Sequence
  • Drug Resistance, Multiple, Bacterial
  • Enterobacter / genetics*
  • Enterobacter / metabolism
  • Enterobacteriaceae Infections / blood
  • Enterobacteriaceae Infections / drug therapy
  • Enterobacteriaceae Infections / microbiology*
  • Gene Transfer, Horizontal
  • Humans
  • Plasmids / genetics*
  • Plasmids / metabolism
  • Whole Genome Sequencing
  • beta-Lactamases / genetics
  • beta-Lactamases / metabolism

Substances

  • Anti-Bacterial Agents
  • Bacterial Proteins
  • beta-Lactamases

Supplementary concepts

  • Enterobacter hormaechei subsp. hoffmannii

Grants and funding

This study was supproted by the Grant-in-Aid for Scientific Research (KAKENHI) of Japan Society for the Promotion of Science (JSPS) under Grant No. JP18K10040 (RK). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.