Purpose: The objective of this study was to determine how bacteriophage resistance in Escherichia coli affects growth and survival in foods, using a model system.
Methods: Bacteriophage T4 E. coli mutants were produced by growing E. coli K-12, in broth culture, in the presence of high concentrations of bacteriophage T4. Bacteriophage resistant mutants were confirmed by spotting the broth cultures on TSA plates, followed by addition of T4 bacteriophage. Colonies that grew in the presence of T4 were isolated and tested for altered biochemical properties using API 20E test strips, and altered susceptibility to the antibiotic kanamycin. In addition, several bacteriophage resistant mutants were evaluated for their ability to grow in beef slurry following an 8-hour incubation at 25°C.
Results: Eight T4 bacteriophage resistant E. coli K-12 mutants (A to H) were isolated. These variants did not display any biochemical changes by API20E or differences in kanamycin susceptibility compared to wild-type K-12. Interestingly, of three mutants tested, one (G) showed no growth in beef slurry after 8 hours.
Significance: These results demonstrate that bacteriophage interactions may alter the fitness of E. coli in foods. These results are important in light of the increasing use of bacteriophages as antimicrobials in foods.