The pathogenicity traits of avian pathogenic Escherichia coli O25-ST131 associated with avian colibacillosis in Georgia poultry and their genotypic and phenotypic overlap with other extraintestinal pathogenic E. coli.

This article focuses on the characterization of Escherichia coli O25 sequence type 131 (O25-ST131), a "global high-risk" clonal strain, isolated from poultry in Georgia, USA. Analysis of 98 avian pathogenic E. coli (APEC) O25 isolates revealed that 88 belonged to ST131 clade b, with many harboring virulence genes typical of both APEC and uropathogenic E. coli (UPEC), indicating genotypic and phenotypic overlap. The isolates demonstrated strong biofilm formation, resistance to chicken serum, growth capability in human urine, and carried multiple antimicrobial resistance genes including extended-spectrum β-lactamases (blaCTX-M-15) and carbapenemases (blaOXA-48), alongside diverse plasmid replicons. These findings suggest that the O25-ST131 clone poses a significant threat to poultry health through colibacillosis and may have zoonotic potential, warranting further investigation into its epidemiology and impact on both animal and human health.