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 10CFU/chip) after BEC8 treatment at MOI of 100 after 10min and at 23°C after 1h on SSC. A similar result was obtained on CTC at 37°C after 10min, and after 1h 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.