Application of lytic bacteriophages OM982647 and OM982646 individually and in combination for mitigating STEC Escherichia coli O157:H7 in milk, yoghurt, and white soft cheese.

Shiga toxigenic Escherichia coli (STEC O157:H7), a significant foodborne pathogen linked to dairy products, cause severe hemorrhagic enteritis in human. Nonetheless, the growing demand for natural, clean label and sustainable biocontrol food safety interventions has highlighted bacteriophages as promising biocontrol agents. In this study, the biocontrol efficacy of two lytic bacteriophages (STEC P2 and STEC P4) individually and in cocktail was evaluated against STEC O157:H7 in various dairy matrices (pasteurized milk, yoghurt, and white soft cheese). Coupled with assessing phages stability in cheese manufacturing conditions, and their potential impact on the starter culture activity. The findings revealed that, the phage cocktail (multiplicity of infection; MOI 106) eliminated STEC in milk within 2 h at 25 °C; however, bacterial regrowth was observed after 12 h. In contrast, at refrigeration temperature (4 °C), STEC P2 and the phage cocktail (MOI 106) reduced STEC below the detection limit within 24 h. In yoghurt, individual phages and their cocktail effectively inhibited STEC by the end of processing, without significantly affecting starter culture activity (P > 0.05). Furthermore, in white soft cheese, the phage cocktail (MOI 106) STEC was not detected by the 7th day of storage at 4 °C. Moreover, both phages exhibited high stability under cheese processing conditions (NaCl (3,5,7%), 0.02% CaCl₂, and 0.04% rennet), nevertheless, reductions of 1.04 and 2.05 log₁₀ PFU were observed for P2 and P4, respectively, during the curd formation phase. These findings demonstrate that STEC P2 and P4 phages, particularly when applied as a cocktail, represent effective sustainable compatible biocontrol agents for mitigating STEC O157:H7 in dairy sector.