Whole-Genome Sequencing Analysis of blaNDM-5/IncX3 Plasmid Estimated to Be Conjugative-Transferred in the Gut.

We characterized plasmids carrying blaNDM-5 detected in Escherichia coli isolated from the infection site and stool sample of a Japanese patient, with no international travel history, by whole-genome sequencing (WGS). WGS was performed using MiSeq and MinlON sequencer followed by hybrid de novo assembly. blaNDM-5 was detected on IncX3 (blaNDM-5/IncX3) plasmids; pMTY18530-4_IncX3 in E. coli TUM18530 isolated from a wound above the pubis; pMTY18780-5_IncX3 and pMTY18781-1_IncX3 in E. coli TUM18780 and TUM18781, respectively, isolated from stool. These three plasmids resembled each other and pGSH8M-2-4, previously detected in E. coli isolated from a Tokyo Bay water sample. E. coli TUM18530 and TUM18780 belonged to sequence type (ST) 1011 and had only two single nucleotide polymorphisms on the core-genome, whereas TUM18781 belonged to ST2040. Three blaNDM-5/IncX3 plasmids (pMTY18530-4_IncX3, pMTY18780-5_IncX3, and pMTY18781-1_IncX3) exhibited conjugative transfer in vitro at an average frequency of 1.71 × 10-3 per donor cell. The transconjugant was resistant to only β-lactams, including carbapenem, except aztreonam. Similarity of the blaNDM-5/IncX3 plasmids isolated from our patient compared with that isolated from the Tokyo bay water sample suggested that the plasmids may have already spread throughout the Japanese community. The blaNDM-5/IncX3 plasmid exhibited potential for easy transmission to different strains in the patient's intestine.