Bacteriophage Cocktail for Biocontrol of Salmonella in Dried Pet Food

Author： Heyse Serena Hanna Leigh Farris Woolston Joelle Sulakvelidze Alexander Charbonneau Duane

Publisher： International Association for Food Protection

E-ISSN： 1944-9097|78|1|97-103

ISSN： 0362-028X

Source： Journal of Food Protection, Vol.78, Iss.1, 2015-01, pp. : 97-103

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Abstract

Human salmonellosis has been associated with contaminated pet foods and treats. Therefore, there is interest in identifying novel approaches for reducing the risk of Salmonella contamination within pet food manufacturing environments. The use of lytic bacteriophages shows promise as a safe and effective way to mitigate Salmonella contamination in various food products. Bacteriophages are safe, natural, highly targeted antibacterial agents that specifically kill bacteria and can be targeted to kill food pathogens without affecting other microbiota. In this study, we show that a cocktail containing six bacteriophages had a broadspectrum activity in vitro against a library of 930 Salmonella enterica strains representing 44 known serovars. The cocktail was effective against 95% of the strains in this tested library. In liquid culture dose-ranging experiments, bacteriophage cocktail concentrations of ≥10⁸ PFU/ml inactivated more than 90% of the Salmonella population (10¹ to 10³ CFU/ml). Dried pet food inoculated with a mixture containing equal proportions of Salmonella serovars Enteritidis (ATCC 4931), Montevideo (ATCC 8387), Senftenberg (ATCC 8400), and Typhimurium (ATCC 13311) and then surface treated with the six-bacteriophage cocktail (≥2.5 ± 1.5 × 10⁶ PFU/g) achieved a greater than 1-log (P < 0.001) reduction compared with the phosphate-buffered saline–treated control in measured viable Salmonella within 60 min. Moreover, this bacteriophage cocktail reduced natural contamination in samples taken from an undistributed lot of commercial dried dog food that tested positive for Salmonella. Our results indicate that bacteriophage biocontrol of S. enterica in dried pet food is technically feasible.