Reduction of Salmonella gallinarum in poultry with phage-based interventions

Salmonella Gallinarum infections (fowl typhoid) cause significant production as well economic losses. We isolated and characterized (viability in simulated gastric fluid and simulated intestinal fluids, host-range, and genomic sequencing) four Salmonella Gallinarum phages to create a phage-based treatment for Salmonella Gallinarum infections in chickens. The phages were distinct based on genomic sequencing and effectively lysed Salmonella Gallinarum strains isolated from diseased chickens in Pakistan. Chicks (7 day-old) were challenged with Salmonella Gallinarum and treated with encapsulated phages or unprotected phages. At 1 and 4 d post-challenge (dpc), cecal Salmonella concentrations of chicks treated with unprotected (4.36 ± 0.20, and 4.02 ± 0.15 log₁₀ CFU/g, respectively) and encapsulated phages (5.05 ± 0.22, and 3.26 ± 0.62 log₁₀ CFU/g, respectively) were significantly lower (P < 0.05) than those of untreated chicks (5.71 ± 0.13, and 4.65 ± 0.08 log₁₀ CFU/g, respectively). In a second animal trial, chicks were challenged with Salmonella Gallinarum but also treated with mixture (1:1) of encapsulated and unprotected phages. At 4 dpc, concentrations of Salmonella Gallinarum in the ceca of chicks treated with any form of phage were significantly lower than those of untreated chicks. At 7 dpc, however, concentrations of Salmonella Gallinarum in the ceca of chicks treated with the mixture of unprotected and encapsulated phages (2.40 ± 0.55 log₁₀ CFU/g) were significantly lower (P < 0.05) than those of chicks in all other treatment groups. Taken together, these data indicate that phage treatment reduces concentrations of Salmonella Gallinarum in experimentally-challenged chickens.