Submitted to: Foodborne Pathogens and Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 2010
Publication Date: February 1, 2011
Repository URL: http://handle.nal.usda.gov/10113/57241
Citation: Callaway, T.R., Edrington, T.S., Anderson, R.C., Poole, T.L., Genovese, K.J., Krueger, N.A., Harvey, R.B., Nisbet, D.J. 2011. Evaluation of phage treatment as a strategy to reduce Salmonella populations in growing swine. Foodborne Pathogens and Disease. 8:261-266. Interpretive Summary: Salmonella causes human illnesses and is found as a member of the intestinal bacterial population of swine. Phages are viruses found naturally in food animals that kill bacteria. We found that the addition of phages that kill Salmonella reduced the intestinal populations of inoculated Salmonella Typhimurium in the cecum and rectum of swine. The number of pigs that were positive for Salmonella in their intestinal contents were significantly decreased. Our results indicate that phages could be a successful preharvest intervention strategy to reduce Salmonella in pigs before they enter the food chain.
Technical Abstract: Salmonella is a foodborne pathogenic bacterium that causes human illnesses, morbidity, and mortality in swine. Bacteriophages are viruses naturally found in food animals that prey on bacteria, and have been suggested as a potential intervention strategy to reduce Salmonella levels in the live animal. The present study was designed to determine if anti-Salmonella phages isolated from the feces of commercial-finishing swine could reduce gastrointestinal populations of the foodborne pathogen Salmonella Typhimurium in an artificially inoculated swine model. Weaned pigs (n = 48) were randomly assigned to two treatment groups (control or phage-treated). Each pig was inoculated with Salmonella Typhimurium (2 x 1010 CFU/pig) via oral gavage at 0 h, and fecal samples were collected every 24 h. Swine were inoculated with a phage cocktail via oral gavage (3 x 109 PFU) at 24 and 48 h. Pigs were humanely sacrificed at 96 h, and cecal and rectal intestinal contents were collected for quantitative and qualitative analysis. Fecal Salmonella populations in phage-treated pigs were lower (P < 0.09) than controls after 48 h. Phage treatment reduced intestinal populations of inoculated Salmonella Typhimurium in pigs compared to controls. Cecal populations were reduced (P = 0.07) more than 1.4 log10 CFU/g digesta and rectal populations (P < 0.10). The number of pigs that contained inoculated Salmonella Typhimurium was reduced by phage treatment, but significance (P < 0.05) was reached only in the rectum. We conclude that phages are a viable strategy to reduce Salmonella in swine before harvest. Further research needs to be performed to determine the most efficacious dosing strategies and the most effective combinations of phages targeting the diverse Salmonella population found in the food supply.