Reduction of Escherichia coli O157:H7 viability on hard surfaces by treatment with a bacteriophage mixture

This study determined the effect of a previously characterized phage mixture, referred as BEC8 on enterohemorrhagic Escherichia coli (EHEC) O157:H7 strains applied on materials typically used in food processing surfaces. Sterile stainless steel chips (SSC), ceramic tile chips (CTC), and high density polyethylene chips (HDPEC) were used. Cultures of EHEC O157:H7 strains EK27, ATCC 43895, and 472 were combined, spot inoculated on surfaces, and dried. Chips were inoculated with 106, 105, and 104CFU/chip, to obtain 1, 10 and 100 multiplicity of infection (MOI) values, respectively. Controls and BEC8 (approx. 106 PFU/chip) were applied on inoculated surfaces and incubated at 4, 12, 23, and 37 °C. EHEC survival was determined using standard plate count on tryptic soy agar. At 37 °C and 12 °C on SSC, no survivors were detected (detection limit 10 CFU/chip) after BEC8 treatment at MOI of 100 after 10 min and at 23 °C after 1 h on SSC. A similar result was obtained on CTC at 37 °C after 10 min, and after 1 h at 23 °C. These results indicated that the phage cocktail was effective within an hour against low levels of the EHEC mixture at above room temperature on all 3 hard surfaces.

Research Highlights
► A novel mixture of phages was applied to food processing surfaces to control E. coli O157:H7.
► Reductions of 4 log CFU were observed at 37 °C if the ratio of viral to bacterial counts was 100.
► Little difference was found among the three food processing surfaces.
► The phage cocktail was effective after 1 h vs. low levels of EHEC at above room temperature.