Phage Preparation for Managing Salmonella in Foods

Non-Technical Summary:<br/>
Salmonellae continue to be one of the leading worldwide causes of foodborne bacterial diseases. They cause 1.2-1.4 million annual cases of salmonellosis in the USA, with associated costs estimated to be as high as $12.8 billion/year (in 1998 dollars). Despite continued and escalating efforts to curb diseases caused by foodborne bacterial pathogens, salmonellae continue to produce foodborne illness at an alarming and increasing rate. In this context, although the overall incidence of foodborne diseases has been declining in the United States, the 2010 report from the FoodNet indicated that the incidence of laboratory-confirmed Salmonella infections continued to increase by approximately 3%, causing 1.2 million U.S. illnesses in that year and being the most common cause of hospitalization and death tracked by the FoodNet. In fact, the incidence of Salmonella-elicited disease during 2010 was nearly 3-fold more than the 2010 national health objective target, and current outbreaks of salmonellosis continue to occur on a regular basis. Moreover, in a disturbing recent development, a Salmonella Typhimurium strain isolated from contaminated ground beef (which was implicated in a multistate outbreak during the fall of 2011) was found to be resistant to several commonly prescribed antibiotics. This is an alarming development because disease caused by such multidrug-resistant strains is associated with an increase in the risk of hospitalization or possible treatment failure in infected individuals. This finding, together with the continuing increase in the incidence of salmonellosis in the United States despite current efforts to curtail that disease, underscores the importance of developing novel intervention strategies and products capable of eliminating or significantly reducing Salmonella in various foods without promoting the emergence of antibiotic-resistant mutants. Any such products should be effective, cheap, safe, environmentally friendly, and easy to use - and there would also be potential advantages for products that target specific Salmonella serotypes; e.g., serotypes predominantly associated with human illness. We believe that a bacteriophage-based preparation/approach may be one such modality. With the partial support from the NIFA USDA Phase I grant, we developed a bacteriophage-based preparation (designated "SalmoFresh") lytic for Salmonella. During our preliminary studies, we found that SalmoFresh consistently and significantly reduced Salmonella levels in various poultry products by as much as 98%. The goals of our currently proposed Phase II project are to (i) obtain additional data concerning the efficacy of SalmoFresh treatment of various foods that are at high risk of Salmonella contamination, and (ii) obtain pertinent regulatory approvals that will enable us to make SalmoFresh available to the food industry and, thus, help to reduce foodborne contamination with Salmonella. We believe that SalmoFresh has the potential to help significantly reduce Salmonella contamination of various foods (including poultry products) and, therefore, to have a significant impact on improving food safety and public health.
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Approach:<br/>
Our proposed project focuses on the development and eventual commercialization of a new product, SalmoFresh, whose active ingredients are naturally occurring, lytic bacteriophages with strong bactericidal activity against selected, "highly pathogenic" serotypes of Salmonella. The approach of using SalmoFresh is based on adding the appropriate concentration of lytic Salmonella bacteriophages directly onto the surfaces of raw poultry products or other foods that are at high risk of Salmonella contamination just before they are sliced and/or packaged. The rationale is that if the foods are contaminated with Salmonella, the phages will eliminate or significantly reduce the concentrations of the bacterium on/in the foods, thus making them safer to eat. The basic concept behind the proposed product and the approach itself is to re-introduce naturally occurring phages back to the foods where they may have come from in the first place; i.e., adding the right phage, in the right concentration, to the right place. Our regulatory approval strategy would be to have SalmoFresh cleared as generally-recognized-as-safe (GRAS) for direct applications on all targeted foods. In keeping with this strategy, the methods we propose to use during our Phase II studies are directly focused on achieving this objective.
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Specifically, we will use standard methods to (1) Develop and validate the optimal production protocol for SalmoFresh, (2) Perform additional studies to determine optimal dosing protocols for eventual commercial product. The efficacy of SalmoFresh treatment will be determined by an (i) enumeration test (during which the levels of Salmonella in foods is determined), and (ii) enrichment-detection test (during which the presence or absence of Salmonella is determined). One-way analysis of variance (ANOVA) and Tukey-Kramer multiple comparisons tests will be used to determine whether treatment with SalmoFresh significantly reduced the number of viable Salmonella on food surfaces contaminated with the test strain. In the enrichment-detection tests, SalmoFresh treatment will be considered effective if the tests reveal significantly more Salmonella-free specimens in the phage-treated group than in the phage-untreated control group treated only with sterile saline or PBS. In the enumeration tests, the treatment will be considered effective if the concentrations of the Salmonella in the phage-treated specimens are significantly lower than in those treated only with sterile saline or PBS. Based on our experience in working with bacteriophages in general, and also on the preliminary data we obtained with SalmoFresh, we fully expect that treatment with SalmoFresh will be effective in reducing or eliminating the Salmonella test strain from the foods we include in our analyses. However, these studies will provide us with critical information re the product's efficacy, and with rigorous data concerning the preferential, optimal application/dosing regimen for SalmoFresh for each targeted food, and (3) Prepare a generally-recognized-as-safe (GRAS) application package for SalmoFresh and submit it to the FDA.