Bacteriophages vs Escherichia coli: A Targeted Approach to Decontaminate Packaged Meat

Antibiotic resistance in avian pathogenic Escherichia coli (APEC) and enterotoxigenic E. coli (ETEC) poses a significant challenge to animal health and food safety. Bacteriophages can specifically target and effectively lyse bacteria, showing promise as an alternative to antibiotics for pathogen control. This study reports on the therapeutic potential of two novel bacteriophages (8A and 9A) that were isolated from chicken/pig faeces using a livestock enteric E. coli isolate as the target/propagation strain. The bacteriophages revealed no activity against 20 each of APEC/ETEC isolates, indicating an extremely narrow host range which may be attributed to the customised strain-specific isolation technique. The bacteriophages have identical capsids (119-120nm) and contractile tails (137-140/20-25nm). Notably, bacteriophage 9A produced halo plaques, suggesting a potential depolymerase activity against capsular bacteria. Based on their distinct plaque properties, the bacteriophages were combined and therapeutically tested in chicken mince and mince broth over 24h. In both food matrices, a single application of the bacteriophage cocktail at combined multiplicity of infection of 10 reduced bacterial growth to undetectable limits, 2h post-treatment at 37oC. Bacterial regrowth was observed afterwards signifying potential resistance effects. Conversely, a significant (p<0.05) bacterial reduction (~4 log10 CFU/mL) was observed at 4-8°C, over the experimental time. This data show that the therapeutic efficacy of the bacteriophages is food matrix- and temperature-dependent, with superior performance in broth at 4-8oC compared to solid mince at 37oC. Genome sequencing, kinetics, stability, formulation and testing in various infection models will further reveal the therapeutic potentials of these bacteriophages in packaging.