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 bla NDM-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 bla NDM-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 bla NDM-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 bla NDM-5 vehicles. Notably, a bla NDM-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 bla NDM-5 dissemination in veterinary settings and further indicate 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.