Emergence of multidrug-resistant and virulent Escherichia coli with APEC‑associated traits in broiler chickens from Ismailia, Egypt

This study investigated Escherichia coli associated with colibacillosis in broiler chickens from two farms in Egypt (April–July 2024). Of the samples collected from diseased birds, 28.5% yielded E. coli, with lesions consistent with systemic infection.

All isolates showed strong pathogenic potential (positive hemolysis and Congo red tests) and were predominantly classified into phylogenetic groups B2, B1, and D. Antimicrobial susceptibility testing revealed universal multidrug resistance (100% MDR), including complete resistance to ampicillin and tetracycline, and very high resistance to cephalosporins (~93%).

Genotypically, resistance was driven mainly by blaTEM and tetA (100%), followed by blaCTX-M and aadA1, while key virulence genes (ompA, iss, iutA) were widely present. A clear correlation was observed between resistance phenotypes, resistance genes, and virulence determinants.

Conclusion:
The high prevalence of MDR, virulent E. coli strains in poultry represents a significant threat to animal health, production economics, and potentially human health via zoonotic transmission. The findings emphasize the need for prudent antimicrobial use, improved biosecurity, and continuous surveillance within a One Health framework.