Emergence of bla_NDM-5-bearing IncHI2/ST2 and p0111 multidrug-resistance plasmids and widespread distribution of IncHI2/ST3-bla_NDM-5 plasmids across foods, animals, and humans

To characterize carbapenemase-producing Enterobacteriaceae (CPE) from vegetables, 185 vegetable samples were collected from farmers' markets and screened for carbapenem-resistant Enterobacterales (CRE). Two Citrobacter freundii and seven Escherichia coli isolates (ST10, ST93, ST206, ST746, ST6736, ST7058, and ST7458) recovered from eight (4.32%) vegetable samples were positive for blaNDM (one blaNDM-1 and eight blaNDM-5). The blaNDM-5 gene was identified on three plasmid types, including IncX3 (n = 2), IncHI2 (n = 4, three ST3-type and one ST2-type), and phage-like p0111 type plasmid (n = 1), while the blaNDM-1 gene was located on IncX3 plasmids. Conjugation experiments confirmed the transferability of all blaNDM-positive plasmids except for the p0111-type plasmid pHNGDSC2239PM-1. Subsequent genomic analysis revealed p0111 and IncHI2/ST2 as two novel blaNDM-5 carrying plasmids vehicles. Notably, the blaNDM-5-carrying IncHI2/ST3 plasmids exhibited high structural similarity to plasmids isolated from diverse sources, and were extensively disseminated in China. The acquisition of the blaNDM-5 gene in the p0111-type plasmid pHNGDSC2239PM-1 was mediated by IS26-flanked pseudocomposite transposons. The capture of blaNDM-5 by the IncHI2/ST2 plasmid pHNBY4G-1 was likely attributed to the homologous recombination events mediated by ISKpn19 and Delta Tn2. Overall, the emergence of blaNDM-5 in IncHI2/ST2 and p0111 plasmids, coupled with the widespread distribution of blaNDM-5-bearing IncHI2/ST3 multidrug-resistance plasmids in animals and foods, indicates a potential for wider dissemination of blaNDM-5, which necessitates attention.