Outbreak and Dissemination of the International High-Risk NDM-5-Producing Escherichia coli ST410 Clone in Companion Animal Hospitals in China

Carbapenemase-producing Enterobacterales (CPEs) have increasingly been detected in companion animals, posing potential risks to both animal and public health. We investigated blaNDM-5-positive Escherichia coli from fecal and environmental samples collected between 2019 and 2025 from 12 companion animal hospitals across six cities in China. A total of 41 blaNDM-5-positive E. coli isolates were recovered from six hospitals, with 36 (87.8%) belonging to sequence type (ST) 410. The 36 E. coli ST410 isolates belonged to B4/H24RxC or B5/H24RxC sub-lineages and displayed close phylogenetic relatedness. Isolates from the same facility differed by only 0–7 cgSNPs, supporting clonal outbreaks. The environmental E. coli ST410 isolate showed 3–7 cgSNPs difference from fecal isolates from the same hospital. Global analysis incorporating 129 pet-derived blaNDM-positive E. coli from GenBank revealed ST410 as the predominant sequence type (38.0%, n = 49). Phylogenetic analysis of 85 pet-derived E. coli ST410 strains from seven countries, incorporating both genomes of our isolates and genomes from GenBank, revealed that they predominantly clustered within B4/H24RxC (n = 35) and B5/H24RxC (n = 47) sub-lineages. These strains were closely related, indicating limited genomic diversity despite wide geographic distribution. Importantly, pet-derived strains shared high genetic similarity (≤ 25 cgSNPs) with human-derived E. coli ST410 isolates, supporting cross-species transmission. Plasmid analysis identified IncX3 and hybrid IncFII/IncFIA/IncFIB plasmids as major blaNDM-5 vehicles. Notably, a blaNDM-5-carrying IncHI2-IncY plasmid was newly detected in companion animals. The frequent occurrence and outbreaks of NDM-5-producing E. coli ST410 in companion animal hospitals highlight its dominant role in blaNDM-5 dissemination in veterinary settings and further indicate that companion animals as reservoirs for high-risk CPE clones. These findings underscore the practical need for strengthened nosocomial infection control, regular environmental disinfection, and integrated AMR surveillance in veterinary hospitals to prevent hospital-acquired infections and their further spread to the community.