Phage Therapy May Reduce Salmonella Infection in Pigs

An anti-salmonella phage cocktail administered to healthy pigs may limit transmission of the bacteria from infected pigs during transport to processing facilities and ultimately minimize the cases of human salmonella food-borne illness. The researchers from Purdue University and USDA ARS, Livestock Behavior Research Unit, West Lafayette, Indiana, report their findings in the January 2010 issue of the journal Applied and Environmental Microbiology.

According to the Centers for Disease Control and Prevention there are approximately 40,000 confirmed human cases of salmonellosis in the United States each year, of which an estimated 400 result in death. Salmonella is transmitted among animals through contact with infected feces. Contamination numbers are often at their highest when healthy and infected animals are housed together in trailers and holding pens on their way to processing facilities, ultimately deterring many on-farm anti-salmonella intervention strategies. Infection and increased shedding of bacteria just prior to entering processing facilities presents a significant problem in terms of food safety.

Phage therapy involves the use of viruses that invade and kill harmful bacterial cells. In a preliminary study researchers inoculated 3 to 4 week-old pigs with salmonella bacteria and then immediately administered the anti-salmonella phage cocktail. Results showed that salmonella colonization was reduced by 99.0 to 99.9% in the tonsils and parts of the small and large intestines. Additionally, they tested the efficacy of phage therapy in a production-like setting by inoculating four market-weight pigs with salmonella bacteria and placing them in a holding pen for 48 hours enabling contamination to occur. Two groups of healthy pigs, one receiving the anti-salmonella phage cocktail and the other a control, were then comingled with the infected pigs in the contaminated pen. Results showed significantly reduced salmonella concentrations in parts of both the small and large intestines.

"The data presented here demonstrate that administering a phage cocktail to pigs prior to exposure to a salmonella-contaminated environment can effectively reduce salmonella colonization in naïve pigs," say the researchers. "We further show that the phage cocktail could be effectively microencapsulated, making feed or water delivery possible."