Immune protection of chickens conferred by a vaccine consisting of attenuated strains of Salmonella Enteritidis, Typhimurium and Infantis

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.

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“…5 Thus, effective control of S. enteritidis infection in poultry is required to maintain healthy poultry flocks and prevent human Salmonellosis. 6 Vaccination is one of the approaches to control S. enteritidis infections 7 and both live attenuated and killed Salmonella vaccines are used to accomplish this goal. [8][9][10] However, under field conditions, these vaccines only marginally decrease, rather than eliminate Salmonella colonization and shedding in the chicken intestine.…”

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“…5 It is strongly believed that controlling Salmonellosis in poultry would reduce human Salmonellosis. 6 Numerous approaches have been tried to control Salmonella shedding in poultry including vaccination. 6 It is expected that Salmonella vaccines decrease intestinal colonization, bacterial shedding in feces, and environmental contamination, thereby reducing the public health risk.…”

“…6 Numerous approaches have been tried to control Salmonella shedding in poultry including vaccination. 6 It is expected that Salmonella vaccines decrease intestinal colonization, bacterial shedding in feces, and environmental contamination, thereby reducing the public health risk. 7 Currently, live-attenuated and killed/subunit vaccines are used to control S. enteritidis.…”

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“…This challenge model is based on a qualitative bacteriological examination of cloacal swabs and internal organs (liver, spleen, caeca, ovary and oviduct) and requires a minimum of 20 animals per group. In contrast, a different challenge model based on quantitative bacteriological examinations of the target organs by tenfold serial dilution of the samples (Koch's spread plate method) has been widely published by numerous authors in the last 3 decades [3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13]. By determining the bacterial burden per gram tissue, this model allows a demonstration of statistically relevant differences between vaccinated and non-vaccinated animals using much lower numbers of animals per group (n = 4–10) [3–13].…”