New research shows that using a modified-live Salmonella Typhimurium (ST) vaccine helps protect broilers against Salmonella Infantis, the most commonly-isolated serotype in chicken parts and comminuted chicken over the last few years¹, and one which can cause salmonellosis in people. However, vaccination alone is not enough to alleviate risk.

“The big driving force for us to do the study was to look at whether we would get good cross-protection with the vaccine against a group C serotype, Salmonella Infantis, that’s an emerging cause of human foodborne illness,” said Charles Hofacre, DVM, PhD, of Southern Poultry Research Group Inc. and one of the authors of the research.

Staged challenge study provides insight

The work, published in the Journal of Applied Poultry Research, began by establishing the optimum dose of S. Infantis to assess internal colonization of broilers at processing age. The researchers concluded that 10⁸ was the ideal for use in this context, with 10⁶ failing to colonize and 10⁹ overwhelming birds.

Then, in a challenge study, three pen experiments were set up. The first two, using 64 birds each, compared the effects of different levels of direct challenge with an S. Infantis field strain on vaccinated and unvaccinated birds. The third explored horizontal — bird to bird — challenge using “seeder” birds inoculated with the pathogen and a total of 1,200 chicks to assess the impact of ST vaccination, which was done at day 1 and day 14 for all birds vaccinated.

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