Salmonella Typhimurium monophasic variant attenuated vaccine is effective in controlling faecal shedding and organ colonization of piglets experimentally challenged

Background: Salmonella Typhimurium and its monophasic variant (S. Typhimurium 1, 4, [5], 12:i-) are increasingly responsible of food borne infections in humans and pork represents the principal source of infection. The aim of the study was to test the efficacy and safety of an attenuated vaccine of S.Typhimurium 1, 4, [5], 12:i- (S. Typhimurium Monophasic variant ΔznuABC). Material and methods: Twenty weaned piglets were divided in 4 groups. Group A (5 piglets) and B (5 piglets) were vaccinated with an oral administration of S. Typhimurium Monophasic variant ΔznuABC at the final dose of 5 х 107 CFU. At day 35 after vaccination, all piglets were challenged by an oral gavage with 5 х 108 CFU of S. Typhimurium Monophasic variant (group A and D) or S. Typhimurium (group B and C). Results and discussion: Vaccine strains were not isolated in faeces after three weeks from vaccination and they did not affect growth of animals, proving a good level of safety. In addition, both attenuated vaccines reduced the colonization of both virulent strains in target organs, in comparison to unvaccinated groups.