Evaluation of a novel cocktail of six lytic bacteriophages against Shiga toxin-producing Escherichia coli in broth, milk and meat

• Published in: Food microbiology 2018-12, Vol.76, p.434-442
• Main Authors: Tomat, David, Casabonne, Cecilia, Aquili, Virginia, Balagué, Claudia, Quiberoni, Andrea
• Format: Article
• Language: English
• Subjects: Escherichia coli; Food safety; Phage cocktail
• ISSN: 0740-0020; 1095-9998
• DOI: 10.1016/j.fm.2018.07.006

Phages are potentially useful as antimicrobial agents in food, especially cocktails of different phages which may prevent the development of bacterial resistance. Biocontrol assays with a six-phage cocktail, which is lytic against DH5α, an enteropathogenic (EPEC) and two Shiga-toxigenic (STEC) Escherichia coli strains, were performed in Hershey-Mg broth, milk and meat at refrigerated (4 °C), room (24 °C) and abusive (37 °C) temperatures. At 4 °C, cell counts were significantly lower (2.2–2.8 log10 CFU/mL) when E. coli strains (∼109 CFU/mL) were challenged against the phage cocktail (∼109 PFU/mL) in Hershey-Mg broth after 24 h. However, reductions were higher (3.2–3.4 log10 CFU/mL) after a 48 h exposure for all the strains tested. In addition, reduction values reached up to 3.4 log10 CFU/mL (24 °C) and 3.6 log10 CFU/mL (37 °C) in challenge tests after 24 h, though the reductions achieved were slightly lower after 48 h for the four E. coli strains tested. In milk, the cocktail was highly effective since bacterial counts were below the detection limit (