Emergence of IncHI2 Plasmid-Harboring blaNDM-5 from Porcine Escherichia coli Isolates in Guangdong, China

Carbapenem resistance has posed potential harmful risks to human and animals. The objectives of this study were to understand the prevalence of bla(NDM-5) in pigs and investigate the molecular characteristics of NDM-5-producing Escherichia coli isolates in Guangdong province in China. Carbapenem-resistant E. coli isolates were isolated from pigs and obtained using MacConkey plates containing 0.5 mg/L meropenem. Conjugation assay and antimicrobial susceptibility testing were conducted for the isolates and their transconjugants. Whole-genome sequence (WGS) was used to analyze the plasmid genetic feature. A total of five bla(NDM-5)-carrying E. coli isolates were obtained in the present investigations. They belonged to five ST types. The bla(NDM-5) genes were found to be in IncX3 and IncHI2 plasmid. The IncX3 plasmid was 46,161 bp in size and identical to other reports. IncHI2 plasmid was 246,593 bp in size and similar to other IncHI2-ST3 plasmids. It consisted of a typical IncHI2 plasmid backbone region and a multiresistance region (MRR). The bla(NDM-5) was closely associated with the IS3000-ISAba125-blaNDM-5-bleMBL-trpF-tat-IS26 unit. We first reported the bla(NDM-5)-carrying IncHI2 in E. coli isolates recovered from pigs and revealed the molecular characterization. Continued surveillance for the dissemination of bla(NDM-5) among food-producing animals is required.