Bacteriophage therapy of human-restricted Salmonella species-a study in a surrogate bacterial and animal model

Salmonella Typhi has been an important human-restricted pathogen from time immemorial, and unfortunately, the indiscriminate use of antibiotics has induced the emergence of multidrug resistance in S. Typhi. Bacteriophage therapy may be a possible alternative in countering antimicrobial resistance. Therefore, this study was planned to assess the efficacy of bacteriophages in treating acute and chronic S. Typhimurium infection in the mouse as a surrogate model. We isolated bacteriophages against S. Typhimurium and selected three different bacteriophages for the in vivo experiments. The lethal dose of S. Typhimurium was decided for Swiss albino mice, and acute infection was developed. Further, bacteriophage therapy by daily intraperitoneal injection of phage cocktail was given for 14 days. While the chronic carrier state of S. Typhimurium in Swiss albino mice was developed by inoculating intraperitoneally sequential 10-fold increasing doses of the bacterium. On the successful establishment of carrier state, oral feeding of phage cocktail at a high count was given, which completely cured the carrier state within 7 days of feeding. These experiments confirmed that the phage cocktail could eradicate the S. Typhimurium from the mice in both types of infections, that is acute and chronic.