Co-occurrence of resistance and virulence plasmids in a blaNDM-5-positive Escherichia coli ST602 clone across One Health sectors in China.

Carbapenem-resistant bacteria circulating across human, animal, and environmental sectors are a growing public health concern. We investigated blaNDM-5-positive Escherichia coli ST602 from an integrated duck-egg farming ecosystem in China using whole-genome sequencing with plasmid characterization. Among 44 representative carbapenem-resistant E. coli (CREC) isolates selected from a larger collection of 103 CREC isolates, seven belonged to ST602 and formed a genetically related O103:H21 cluster recovered from human, duck, and environmental samples within the same farm ecosystem. To place these isolates in context, we analyzed a curated global dataset of 628 ST602 genomes. The local ST602 isolates clustered within a phylogroup B1 O103:H21-associated subclade in a global dataset dominated by European and North American genomes. In all seven isolates, blaNDM-5 was carried on conjugative IncHI2/IncHI2A plasmids with a conserved IS5-blaNDM-5-ble-trpF-IS26 structure. The same isolates co-harbored a non-conjugative IncFIB/IncFIC(FII) plasmid carrying virulence-associated genes (iutA, iroBCDEN, iucABCD, hlyF, iss, traT) together with additional resistance determinants. Comparative analyses also indicated enrichment of genes encoding bacteriocins and recurrent co-occurrence patterns between blaNDM-5 and other resistance genes. These findings further document a genetically related O103:H21-ST602 cluster within a duck-farm One Health setting that co-harbors transferable carbapenem resistance and conserved virulence-associated plasmids, underscoring the need for integrated genomic surveillance of locally emerging CREC lineages.