Abstract
The colonization of poultry with different Salmonella enterica serovars poses an issue throughout the world. In this study we therefore tested the efficacy of a vaccine consisting of attenuated strains of Salmonella enterica serovars Enteritidis, Typhimurium and Infantis against challenge with the same serovars and with S. Agona, Dublin and Hadar. We tested oral and aerosol administration of the vaccine, with or without co-administration of cecal microbiota from adult hens. The protective effect was determined by bacterial counts of the challenge strains up to week 18 of life and by characterizing the immune response using real-time PCR specific for 16 different genes. We have shown that a vaccine consisting of attenuated S. Enteritidis, S. Typhimurium and S. Infantis protected chickens against challenge with the wild type strains of the same serovars and partially protected chickens also against challenge with isolates belonging to serovars Dublin or Hadar. Aerosol vaccination was more effective at inducing systemic immunity whilst oral vaccination stimulated a local immune response in the gut. Co-administration of cecal microbiota increased the protectiveness in the intestinal tract but slightly decreased the systemic immune response. Adjusting the vaccine composition and changing the administration route therefore affects vaccine efficacy.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-016-0371-8) contains supplementary material, which is available to authorized users.
Highlights
Introduction the incidence of human salmonellosis is gradually decreasing in the EU, Salmonella enterica is still one of the most frequent causative agents of gastroenteritis in humans worldwide [1]
Since the major reservoirs of Salmonella enterica for human populations are found in poultry flocks [2], it is expected that a decrease in Salmonella prevalence in poultry will result in a decrease in the incidence of human salmonellosis
Full genome sequencing confirmed the presence of all mutations as designed and the absence of any additional difference between the wild type strain and appropriate mutant
Summary
The incidence of human salmonellosis is gradually decreasing in the EU, Salmonella enterica is still one of the most frequent causative agents of gastroenteritis in humans worldwide [1]. Since the major reservoirs of Salmonella enterica for human populations are found in poultry flocks [2], it is expected that a decrease in Salmonella prevalence in poultry will result in a decrease in the incidence of human salmonellosis. One of the most feasible ways of reducing Salmonella prevalence in poultry flocks is vaccination. Current live attenuated vaccines and vaccination schemes, though effective, exhibit several limitations. Live commercial vaccines for poultry are available for S. enterica serovars Enteritidis, Typhimurium and Gallinarum only, Rapid vaccination soon after hatching can be achieved by spraying. There are several reports on aerosol administration of live Salmonella vaccines to chickens
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