Poultry pathogenicity, antimicrobial resistance, and one health genomic characterization of ST83 Escherichia coli.

Escherichia coli is a clinically relevant zoonotic pathogen with significant impacts on both food safety and animal/human health. This study characterized the pathogenicity and genomic features of sequence type (ST) 83 E. coli isolated from liver samples of deceased chicken in China, along with its potential for zoonotic transmission. A total of eight ST83 E. coli isolates were obtained from liver samples. Pathogenicity tests demonstrated the isolates’ virulence in chickens, inducing significant pathological lesions indicative of poultry health risks. Genomic analysis indicated an alarming antimicrobial resistance gene (ARG) profile, including tet(X4) and blaNDM−5, among ST83 E. coli strains in China. The ARGs were strongly associated with mobile genetic elements (MGEs) such as IncQ1 plasmids and insertion sequences (ISs) IS903, highlighting their co-transmission potential through horizontal gene transfer. In addition, core genome phylogeny and pangenome analysis identified minimal genetic divergence between human- and animal-derived strains. This close relationship, evidenced by shared accessory genes and small SNP differences, suggests potential zoonotic transmission. Collectively, these findings indicate that ST83 E. coli is a dual-threat pathogen, being not only a virulent pathogen in poultry but also a One Health concern due to its potential for zoonotic transmission and antimicrobial resistance dissemination.