IV Jornadas Latinoamericanas de Bacteriófagos

Avian pathogenic Escherichia coli (APEC) is a widespread pathogen that causes colibacillosis in poultry, resulting in high mortality, significant economic impact. APEC control with antibiotics increases the prevalence of multidrug-resistant strains. Bacteriophage-based cocktails are emerging as promising alternatives to antibiotics for controlling APEC under commercial farm conditions. In this study, we isolated and sequenced 142 APEC strains from Brazilian broiler farms, as well as 66 lytic bacteriophages. Eight phages with complementary host ranges were selected to assemble a four-phage cocktail, and these phages were sequenced and characterized. Quantitative in vitro assays demonstrated that the phage cocktail inhibited 56.3% of the isolates, with higher activity against high-risk APEC. Additionally, the formulated cocktail was also tested in combination with two commonly used antibiotics in farms. The phage cocktail exhibited additive effects with trimethoprim-sulfadimidine, while synergistic effects with florfenicol. These results highlight the potential of phage cocktails designed for high specificity and antibiotic compatibility as effective tools to control APEC in commercial poultry production, supporting their future application under farm conditions.