Evaluation of the in vitro and in vivo efficiency of in-feed bacteriophage cocktail application to control Salmonella Typhimurium and Salmonella Enteritidis infection in broiler chicks.

The application of bacteriophages (BP) could be a possible method to control poultry salmonellosis. However, the sensitivity of field isolates to different phages can restrict their application in the poultry industry. In this survey, the sensitivity of 20 Salmonella field isolates including 10 S. Typhimurium and 10 S. Enteritidis to a bacteriophage cocktail was evaluated. The investigated BP cocktail had a promising lytic effect on all field isolates in this survey. The lytic activity of the BP cocktail was retained at different pH values (5.5-8) and temperatures (25℃ and 37℃ for 48 hours; 55°C for 10 min). Physico-chemical resistance of the BP cocktail indicated that it has the potential to be used as a feed additive to control Salmonella contamination. The BP cocktail in feed contaminated with S . Enteritidis and S . Typhimurium showed a significant reduction effect on colonization of Salmonella in the liver, crop, spleen, and caeca of the broilers at 7,14 and 21 days.