A Lytic Bacteriophage as a Potential Biocontrol Agent Against Avian Enterotoxigenic Escherichia coli Associated With Colibacillosis.

Introduction: Diarrheal diseases remain a major public health concern, causing over two million deaths annually in developing countries. Diarrheagenic Escherichia coli, particularly enterotoxigenic strains, are a leading cause of gastrointestinal infections in humans and animals. Poultry can act as a reservoir for pathogenic E. coli, facilitating transmission to humans via contaminated food or water. This study aimed to isolate and characterize bacteriophages targeting E. coli pathotypes from poultry, with the goal of controlling gastrointestinal infections and reducing the risk of zoonotic transmission. Methods: ETEC strains were isolated from poultry with colibacillosis and confirmed by LT and ST toxin genes. Their antibiotic resistance and biofilm formation were evaluated. Bacteriophages were isolated from wastewater, and their host range, morphology, growth characteristics, lytic activity, and stability under different temperatures and pH were assessed. Result: The isolated ETEC strain exhibited a multidrug-resistant phenotype and strong biofilm formation. The bacteriophage was highly specific for this strain, showing no lysis of other bacteria, and was classified as belonging to the Autographiviridae family by TEM analysis. One-step growth experiments revealed a latent period of 0-10 min and a burst size of 93 PFU/cell. Lytic activity was effective at MOIs of 10 and 100, and the phage remained stable under typical environmental and physiological conditions, suggesting its potential applicability in poultry. Conclusion: The isolated phage demonstrates high specificity, lytic activity, and stability, indicating its potential as an alternative or adjunct to antibiotics for controlling MDR ETEC in poultry. Further studies are warranted to evaluate its safety and efficacy under in vivo conditions.