Isolation and characterization of phages that can be used in the inhibition of escherichia coli O157:H7 and salmonella typhimurium by phage therapy method in foods

Infections caused by foodborne pathogens lead to many diseases, chronic complications and epidemics that cause one-third of the deaths in the world. Among the main causes of these deaths are Escherichia coli and Salmonella spp., which are the leading foodborne pathogens types are shown. Excessive and unconscious use of antibiotics has led to the emergence of antimicrobial resistance in Salmonella spp. and E. coli O157:H7 species. With the increasing antibiotic resistance worldwide, the use of phages as biocontrol elements in food, environment and medicine has accelerated again. Bacteriophage applications are also an effective tool in food preservation and safety. Phage cocktails are applied to decontaminate food preparation surfaces and at different points of the food processing facility and food chain to reduce the level of Salmonella Typhimurium, E. coli O157:H7 contamination. In this study, 13 bacteriophages showing high lytic activity against S. Typhimurium and E. coli O157:H7 were isolated from 24 raw cow's milk collected from various villages of Bolu province. After these isolated phages were purified and their titers reached 108 PFU/mL, their DNAs were isolated and their RFLP profiles were determined. Among the phages divided into groups according to their restriction profiles, S. Typhimurium Ssüt12.2.2, Ssüt16.1.1, Ssüt10.2.4, Ssüt10.1.1 phages with the highest titers and E. coli O157:H7 E12.2.1, E13.2.1 and E13.3.2 phages were selected and characterized. To characterize these phages, infection abundances, host ranges, latent periods and burst sizes were determined. Two separate phage cocktails were prepared for the characterized E. coli O157:H7 and S. Typhimurium phages, and the effectiveness of the phages on E. coli O157:H7 and S. Typhimurium was determined in the coconut milk sample. The results obtained showed that the phage cocktail completely eliminated the presence of pathogens in the environment at an MOI (Multiplicity of Infection): 1000.