Phage Inhibition ofEscherichia coliin Ultrahigh-Temperature-Treated and Raw Milk

Abstract

Escherichia coli can contaminate raw milk during the milking process or via environmental contamination in milk-processing facilities. Three bacteriophages, designated EC6, EC9, and EC11, were investigated for their ability to inhibit the growth of three strains of E. coli in ultrahigh-temperature (UHT) treated and raw bovine milk. A cocktail of the three phages completely inhibited E. coli ATCC 25922 and E. coli O127:H6 in UHT milk at 25 °C and under refrigeration temperatures (5-9 °C). The phage cocktail produced similar results in raw milk; however, E. coli ATCC 25922 and O127:H6 in raw milk controls also declined to below the level of detection at both temperatures. This observation indicated that competition by the raw milk microbiota might have contributed to the decline in viable E. coli cells. A cocktail containing EC6 and EC9 completely inhibited E. coli O5:H-, an enterohemorrhagic strain, in UHT milk at both temperatures. In raw milk, the phage cocktail initially inhibited growth of E. coli O5:H- but regrowth occurred following incubation for 9 h at 25 °C and 144 h at 5-9 °C. In contrast to the other E. coli strains, O5:H- was not inhibited in the raw milk controls. This study demonstrates that bacteriophages are effective biocontrol agents against E. coli host strains in UHT and raw bovine milk at various storage temperatures.

HostPhinder: A Phage Host Prediction Tool

“…Phages have furthermore been suggested for use in the agriculture and food industries [ 16 , 17 ]. Examples include their use for reducing Campylobacter jejuni colonisation of broiler chickens [ 18 ] and the growth of E. coli in milk [ 19 ].…”

Bacteriophage Applications for Food Production and Processing

“…Recent work has demonstrated that E. coli -specific phage preparations were effective when used to treat fresh vegetables [ 75 ] and both Ultra-High-Temperature (UHT) treated and raw milk contaminated with E. coli [ 33 ]. In the first study, the levels of E. coli O157:H7 on green pepper slices and spinach leaves were reduced by a single phage by ~1–4 logs, and the initial reduction was maintained at 4 °C while some regrowth was seen at 25 °C.…”

“…Phage biocontrol provides an effective tool for improving food safety, but it does not eliminate the need for safe food handling practices. For example, regrowth of bacteria was observed after phage treatment if the foods are stored at abuse temperatures [ 33 , 48 , 54 ]. Also, some planning is required to maintain optimal efficacy of phage biocontrol when combining bacteriophages with some other food safety interventions, such as using phages in conjunction with chemical sanitizers [ 59 ].…”

The use of bacteriophages to control and detect pathogens in the dairy industry

“…Consumption of raw milk and raw milk products has been associated with many cases of E. coli ‐related illness (Mungai et al ). A mixture of three coliphages was shown to eradicate two strains of E. coli in raw milk, both at 25 °C where the cells are metabolically active, and also during extended refrigerated storage (McLean et al ). In another study, Tomat et al () used phages to significantly reduce E. coli 0157:H7 during milk fermentations for yoghurt production.…”