Protection conferred by a Salmonella-based subunit vaccine against S. Infantis in broilers

JOAQUIM P.; LAYTON S.; VECCHI B.; SUGEZKY, A.; CHACANA P.

Atlanta

Seminario; INTERNATIONAL PRODUCTION & PROCESSING EXPO?; 2018

Salmonella infection is a major cause of bacterial enteric illness in both human and animals and poultry production is usually associated with the contamination of this food-borne pathogen. Several serotypes are worldwide isolated from poultry, mainly S. Enteritidis, S. Typhimuirum, S. Infantis and S. Heidelberg among others. Nowadays, vaccination is one of the main strategies to control Salmonella in the farms and to avoid the use of antimicrobials and to improve the food safety for the consumers. In previous trials, efficacy of a Salmonella-based subunit vaccine to protect against S. Enteritidis (SE) was assed and the aim of this work was to evaluate the performance of the vaccine against S. Infantis (SI). One-day old broiler chicks were divided into vaccinated and unvaccinated groups. Twenty-two birds from vaccinated groups were individually administered a Salmonella-based subunit vaccine by oral instillation at day 3 and 17 of life whereas 27 chickens from unvaccinated group only received PBS. At day 30 all birds were challenged by oral gavage with 109 CFU of a virulent strain of SI and individual samples were taken by cloacal swabbing at the 4thand 8th day post-infection (dpi) to determine the excretion of the microorganism. Samples were enriched using tetrathionate broth and thereafter detection of the strain was done on XLD agar plates. Additionally, at the 8th dpi enumeration of Salmonella in caecal contents was done in 5 birds from each group. At the 4th dpi 21/27 (77%) and 8/22 (36%) birds respectively from unvaccinated and vaccinated groups were positive for Salmonella; whereas at 8th dpi the microorganism was recovered from 7/27 (26%) of the unvaccinated chicken and from none of vaccinated birds (0/22). The pathogen was isolated from 4/5 of the caecal contents samples from unvaccinated birds (average enumeration: 102,4 CFU/gram) but could not be isolated from any of the caecal contents of the vaccinated chicken (0/5). The vaccine was able to reduce the excretion and caecal colonization of SI. These results were similar to those obtained previously when chickens were challenged with SE, demonstrating the efficacy of the vaccine to control several serotypes of Salmonella, even when they belong to different serogroups. Application of the vaccine in the farms combined with appropriate biosecurity management may be a useful tool to control Salmonella by reducing the infection of the birds and the contamination of the environment.