Dissemination of <i>bla</i> _NDM-5 in <i>Escherichia coli</i> through the IncX3 Plasmid from Different Regions in China

Abstract

The spread of NDM-5-producing <i>Escherichia coli</i> has become a severe challenge in clinical therapy, which necessitates reliable detection and surveillance methods. However, limited information is available regarding the prevalence and dissemination of the <i>bla</i>_NDM-5 gene in <i>E. coli</i> in China. Therefore, we investigated the dissemination of the <i>bla</i>_NDM-5 gene in carbapenem-resistant <i>E. coli</i> isolates from different regions. A total of 1,180 carbapenem-resistant enterobacteriaceae strains were obtained from patients admitted to the 20 sentinel hospitals in 8 cities. Strains positive for <i>bla</i>_NDM-5 were detected using the Vitek 2 compact system, 16S ribosomal RNA (rRNA) gene sequencing, polymerase chain reaction, the S1 pulsed-field gel electrophoresis assay, and Southern blot hybridization. The horizontal-transfer capability of the <i>bla</i>_NDM gene was assessed by filter mating with a standard <i>E. coli</i> J53 azide-resistant strain as the recipient. Genotyping, susceptibility testing, and whole genome sequencing were performed. Seven strains of <i>bla</i>_NDM-5-positive <i>E. coli</i> were detected in 1,180 clinical strains from different regions in China. The <i>bla</i>_NDM-5-carrying strains showed resistance to multiple tested antibiotics and belonged to two widespread sequence types, sequence type (ST)167 and ST405. Antimicrobial resistance genes, including <i>bla</i>_CTX-M, <i>bla</i>_OXA, <i>bla</i>_CMY, and two novel <i>bla</i>_TEM variants (<i>bla</i>_TEM-230 and <i>bla</i>_TEM-231) were also identified. Southern blotting located the <i>bla</i>_NDM-5 gene on 46 kb IncX3 plasmids in all isolates, which showed only two single nucleotide differences between EJN003 and the other strains. This study further confirms the increasing occurrence of <i>bla</i>_NDM-5-carrying IncX3 plasmids and the dissemination of carbapenem resistance in <i>E. coli</i> isolates using the plasmid from different parts in China, which warrants stringent surveillance and control measures.