ARS | Publication request: Phage therapy reduces lairage-induced increases in Salmonella colonization in market weight pigs

Submitted to: International Association for Food Protection
Publication Type: Proceedings
Publication Acceptance Date: February 10, 2009
Publication Date: N/A

Technical Abstract: Contamination of meat and meat products with foodborne pathogens usually results from the carcass coming in contact with the feces of an infected animal during processing. In the case of Salmonella, several recent studies have reported that pigs become rapidly infected with the organism during transport and lairage due to contaminated trailers and holding pens. These infections serve to increase the likelihood of carcass contamination by amplifying the amount of bacteria that enters the processing facility, increasing food safety risk. We conducted a series of experiments to test whether phage therapy could be used to counteract Salmonella infections at this critical pre-slaughter period. Fourteen anti-Salmonella phage were isolated from wastewater treatment facilities and characterized by electron microscopy. In a preliminary experiment, microencapsulated phage were co-administered with Salmonella enterica Typhimurium to 4-5 week-old pigs. In the main experiment designed to mimic a production setting, microencapsulated phage were administered to market weight pigs prior to their comingling with Salmonella enterica Typhimurium infected pigs in a contaminated pen. Treating the small pigs with the phage cocktail at the time of inoculation with Salmonella enterica Typhimurium reduced the extent of Salmonella colonization by 99.0-99.9% (2-3 log growth) in the tonsils, ileum, and cecum as compared to mock-treated pigs. Under production-like settings, treatment of market weight pigs with the anti-Salmonella phage cocktail significantly reduced cecal Salmonella counts (95%, P < .05) while also showing a strong tendency to reduce ileal Salmonella counts (90%, P = .06). In vitro studies demonstrated that the phage cocktail was also effective at lysing several non-Typhimurium Salmonella serovars. Taken together, these data indicate that phage therapy can be used as an effective anti-Salmonella intervention strategy to prevent lairage-associated increases in Salmonella colonization in pigs.