Dissemination of Blandm-5 in Escherichia Coli via the Incx3 Plasmid From Different Regions in China

Background: Recently, the spread of NDM-5-producing Escherichia coli 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 bla NDM-5 gene in Escherichia coli in China. Therefore, we investigated the dissemination of the bla NDM-5 gene in carbapenem-resistant Escherichia coli isolates from different regions in China. Methods: : A total of 1,180 carbapenem-resistant enterobacteriaceae strains were obtained from patients admitted to the 20 sentinel hospitals in eight cities. Strains positive for bla NDM-5 were detected using the Vitek 2 compact system, 16S rRNA gene sequencing, PCR, the S1-pulsed-field gel electrophoresis assay, and Southern blot hybridization. The horizontal-transfer capability of the bla NDM gene was assessed by filter mating with a standard E. coli J53 azide-resistant strain as the recipient. Genotyping, susceptibility testing, and whole genome sequencing were performed. Results: : Seven strains of bla NDM-5 -positive E.coli was detected in 1180 clinical strains from different regions in China. The bla NDM-5 -carrying strains showed resistance to multiple tested antibiotics and belonged to two widespread sequence types, ST167 and ST405. Antimicrobial resistance genes including bla CTX-M , bla OXA , bla CMY , and two novel bla TEM variants ( bla TEM-230 and bla TEM-231 ) were also identified. Southern blotting located the bla NDM-5 gene on 46-kb IncX3 plasmids in all isolates, which showed only two single nucleotide differences between EJN003 and the other strains. Conclusions: : This study further confirms the increasing occurrence of bla NDM-5 -carrying IncX3 plasmids and the dissemination of carbapenem resistance in E. coli isolates via the plasmid from different parts in China, which warrants stringent surveillance and control measures.