LANGFORD, U.K.—Enteric infection from food-borne organisms like Salmonella presents a significant public health risk around the world, and according to the USDA, salmonellosis cost the U.S. economy more than $2.3 billion in 2005. With the growing concern over chemical additives in food, however, researchers at the University of Bristol, Wageningen UR, and the Institute for Animal Health relied on a natural enemy of infectious bacteria—the bacteriophage (or phage)—to treat chickens before they entered the food system.
As they report in Applied and Environmental Microbiology, the researchers isolated more than 200 strains of Salmonella phage from 26 sampling sites such as broiler farms, abattoirs, and wastewater plants. They then characterized three phages that showed the broadest host range against one of S. enteritidis, S. hadar, or S. typhimurium. In vitro, each phage was able to significantly reduce the titers of its bacterial target, but the in vivo results were initially less promising.
Dosing infected chickens with phage in antacids, the researchers found that lower phage doses were relatively ineffective at reducing bacterial levels in the chicken ceca. They speculated that this might be due to the complex content of the chicken digestive tract, which would include "decoy" bacteria and particulate matter. At higher doses, however, the S. typhimurium and S. enteritidis phage were quite effective, reducing bacterial titers several logs. The S. hadar phage was still relatively ineffective.
The researchers speculated that a better understanding of phage-host interaction might help them identify better phage therapeutics and that a cocktail of phages attaching to different host receptors might be more efficacious and offset concerns over phage resistance.