Bacteriophage control of foodborne bacteria

Bacteriophages are measurable components of the natural microflora in the food production continuum from the farm to the retail outlet. Phages are remarkably stable in these environments and are readily recovered from soil, sewage, water, farm and processing plant effluents, feces, and retail foods. Purified high-titer phage lysates have been used for the species-specific control of bacteria during the pre- and postharvest phases of food production and storage. For example, the inhibition of the phytopathogens Erwinia amylovara and Xanthomonas campestris has reduced the incidence of diseases such as fire blight in apples and bacterial spot of tomato and peaches. Research on preslaughter treatment of food animals has demonstrated phage control of salmonellosis in chickens, enteropathogenic Escherichia coli infections in calves, piglets, and lambs, and E. coli O157:H7 shedding by beef cattle. Phages have also been applied to control the growth of pathogens such as Listeria monocytogenes, Salmonella, and Campylobacter jejuni in a variety of refrigerated foods such as fruit, dairy products, poultry, and red meats. Phage control of spoilage bacteria (e.g., Pseudomonas spp. and Brochothrix thermosphacta) in raw chilled meats can result in a significant extension of storage life. Phage biocontrol strategies for food preservation have the advantages of being self-perpetuating, highly discriminatory, natural, and cost-effective. Some of the drawbacks of biopreservation with phages are a limited host range, the requirement for threshold numbers of the bacterial targets, phage-resistant mutants, and the potential for the transduction of undesirable characteristics from one bacterial strain to another. Most research to date has involved experimentally infected plants and animals or artificially inoculated foods. This technology must be transferred to the field and to commercial environments to assess the possibility of controlling natural contaminants under more realistic production and processing conditions.