Effect of phage and host concentration on the inactivation of Escherichia coli O157:H7 on cooked and raw beef

• Published in: Food science and technology international Vol. 21; no. 2; p. 104
• Main Authors: Hudson, J A, Billington, C, Wilson, T, On, S L W
• Format: Journal Article
• Language: English
• Published: United States 01.03.2015
• Subjects: Animals; Bacteriophages; Cattle; Colony Count, Microbial; Cooking; Escherichia coli O157 - growth & development; Food Handling - methods; Food Microbiology; Food Preservation - methods; Food Storage; Humans; Microbial Viability; Red Meat - microbiology; Temperature; food safety; bacteriophage; biocontrol; Escherichia coli O157:H7
• ISSN: 1532-1738
• DOI: 10.1177/1082013213513031

A previously described phage infecting Escherichia coli O157:H7 was added to raw and cooked beef pieces at concentrations ranging from 10(1)-10(8) plaque forming units/cm(2) to either low (<100 CFU/cm(2)) or high (10(4) CFU/cm(2)) concentrations of host bacterial cells. Incubation for up to 24 h was performed at 5 ℃ and 24 ℃ to simulate refrigerated and room temperature storage/temperature abuse. Surviving bacteria were enumerated during the incubation period, with phages being counted at the first and last sampling times. Significant reductions of E. coli O157:H7 of the order of >4 log10 CFU/cm(2) at both temperatures could be achieved compared to phage-free controls. There was a trend for greater inactivation to occur with increasing phage concentration. While re-growth of surviving cells occurred in nearly all samples incubated for 24 h at 24 ℃, these conditions are not typical of those experienced by perishable foods. It was concluded that phages can be used to reduce the concentration of a bacterial pathogen on meat, but the concentration of phages needs to be high (>4-5 log10 plaque forming units/cm(2)) for reductions to occur. A concentration of the order 8 log10 plaque forming units/cm(2) was needed to achieve a 4 log10 CFU/cm(2) reduction.