Biocontrol of Salmonella Schwarzengrund and Escherichia coli O157:H7 planktonic and biofilm cells via combined treatment of polyvalent phage and sodium hexametaphosphate on foods and food contact surfaces

Salmonella Schwarzengrund and Escherichia coli O157:H7 are ones of foodborne pathogens that can produce biofilms and cause serious food poisoning. Bacteriophages are an emerging antibacterial strategy used to prevent foodborne pathogen contamination in the food industry. In this study, the combined antibacterial effects of the polyvalent phage PS5 and sodium hexametaphosphate (SHMP) against both pathogens were investigated to evaluate their effectiveness in food applications. The combined treatment with phage PS5 (multiplicity of infection, MOI = 10) and 1.0% SHMP inhibited the growth of S. Schwarzengrund and E. coli O157:H7, and the viable counts of both decreased by more than 2.45 log CFU/mL. In KAGOME vegetable and fruit mixed juice, the combined treatment with PS5 (MOI = 100) and 1.0% SHMP also resulted in significant pathogen inactivation at 4 °C after 24 h. PS5 (10¹⁰ PFU/mL) and 1.0% SHMP showed stronger synergistic effects on biofilm formation and the removal of established biofilms on polystyrene plates. Additionally, we evaluated their combined effects on reducing the biofilms of S. Schwarzengrund and E. coli O157:H7 on glass tubes and cabbage leaves at 4 °C. These findings indicate the utility of this approach in the biocontrol of the planktonic and biofilm cells of S. Schwarzengrund and E. coli O157:H7 on foods and food contact surfaces.