Coevolution of Bacteriophages Enhances Biocontrol of Shiga Toxin-Producing Escherichia coli in Food Matrix

Shiga toxin-producing Escherichia coli (STEC) are major foodborne pathogens responsible for severe illnesses such as hemorrhagic colitis (HC) and hemolytic-uremic syndrome (HUS). Transmission commonly occurs through undercooked meat, raw dairy products, and fresh vegetable products, with ruminants identified as the primary reservoirs (EFSA, 2020), posing an increasing threat to public health. This study investigates the potential of bacteriophages as biocontrol agents, specifically examining the impact of coevolutionary training to enhance phage efficacy against bacterial resistance mechanisms. A lytic bacteriophage isolated from breeding farms (Mangieri et al., 2020) was coevolved over 25 sequential cycles with different STEC strains, including O157 and non-O157 serogroups. The "trained" phage was characterized and tested both in vitro and in a food matrix. Compared to its wild-type, the trained phage exhibited improved suppression of STEC growth. When applied to fresh vegetables in challenge tests, the trained phage significantly reduced STEC populations. These results underscore the value of phage coevolution as a proactive strategy to improve phagebased biocontrol of STEC in food applications.