Molecular epidemiology and genomic insights into the transmission of carbapenem-resistant NDM-producing .

is a leading cause of nosocomial infections. Carbapenem-resistant (CREC), which has been frequently isolated in recent years because of the widespread use of carbapenems, poses a significant challenge to clinical anti-infection treatment. In this study, a total of 27 CREC strains were identified from a set of 795 isolates collected over a two-year period from a tertiary hospital in China. Whole-genome sequencing revealed that 17 strains carried the gene, 5 strains carried the gene, 1 strain carried the gene, and the remaining 4 strains carried the gene. All 23 NDM-producing strains were resistant to all antibiotics except tigecycline, colistin, and cefiderocol. Nine different sequence types (STs) were identified, with ST410 and ST167 being the most prevalent. All of the genes were located on conjugatable plasmids. We identified five different plasmid replicon types ranging in size from 20 kb to 200 kb, with the IncX3-type plasmid, 46 kb in size, being a key factor in facilitating the horizontal transmission of the gene in . The structure surrounding the gene was relatively conserved and mainly contained the following structures: IS-IS-IS- - ---IS. However, the plasmid backbone structure was highly variable, which indicates that the gene has already spread horizontally among different types of plasmids. In addition, we discovered two copies of the gene in a single plasmid (pEC29-NDM-5), with an identical structure around the gene and the complete sequence of the class 1 integron. Our findings detail the prevalence of CREC in a tertiary hospital in China, and the emergence of multiple copies of the gene on a single plasmid needs our attention.