Reduction of Salmonella gallinarum in poultry with phage-based interventions.

Abstract

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&#xa0;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&#x2009;&#xb1;&#x2009;0.20, and 4.02&#x2009;&#xb1;&#x2009;0.15 logCFU/g, respectively) and encapsulated phages (5.05&#x2009;&#xb1;&#x2009;0.22, and 3.26&#x2009;&#xb1;&#x2009;0.62 logCFU/g, respectively) were significantly lower (P&#x2009;<&#x2009;0.05) than those of untreated chicks (5.71&#x2009;&#xb1;&#x2009;0.13, and 4.65&#x2009;&#xb1;&#x2009;0.08 logCFU/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&#x2009;&#xb1;&#x2009;0.55 logCFU/g) were significantly lower (P&#x2009;<&#x2009;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.