Vaccination of turkeys against Salmonella enterica serovar Infantis: effects on the cecal microbiome and tissue colonization

Authors: Monson, Melissa; GURUNG, MANOJ - Oak Ridge Institute For Science And Education (ORISE); Trachsel, Julian; Bearson, Bradley - Brad; Looft, Torey; Bearson, Shawn

Submitted to: Avian Immunology Research Group Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 9/28/2022
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Salmonella enterica serovar Infantis has emerged as a prominent serovar in poultry, recently contributing to outbreaks of human foodborne illness in the USA. Vaccination against Salmonella is an important strategy in turkey production to reduce food safety risk to humans, but better understanding of the effects of vaccination on S. Infantis in turkeys is still needed. Oral vaccines can change the microbiome through both direct effects of the vaccine strain on the intestinal microbiota and activation of the host mucosal immune response, which can influence the bacterial communities colonizing the gastrointestinal tract. Thus, 16S rRNA gene sequencing of the microbiome was used to investigate the effects of two vaccines, a cross-protective vaccine BBS 866 and the commercial vaccine AviPro Megan Egg®, in turkeys subsequently challenged with S. Infantis. One day old domestic turkey poults were randomly divided into four groups and vaccinated by oral gavage with 109 colony forming units (CFU) of BBS 866 vaccine or AviPro vaccine, or mock-vaccinated with an equivalent volume of PBS (two groups). Poults were booster vaccinated at three weeks of age, and four weeks later, cecal contents were collected (n = 10-12 birds/group) to evaluate the effects of immunization on the turkey microbiome. At seven weeks of age, three groups were orally challenged with 109 CFU of an outbreak-associated S. Infantis strain (SX 500), while one mock-vaccinated group was gavaged with PBS. Cecal tonsil tissue and cecal contents were collected (n = 12-14 birds/group) at 10 days post-inoculation. Compared to the mock-vaccinated/S. Infantis-challenged turkeys, both vaccines significantly decreased S. Infantis colonization of the cecal tonsil, yet Salmonella load within the cecal contents was higher in vaccinated turkeys. Cecal microbiome structure was distinct in each vaccinated and mock-vaccinated group prior to S. Infantis challenge, with greater diversity (Shannon and PERMANOVA) in the AviPro group relative to the mock vaccinates than the BBS 866 group. Alpha diversity (Shannon) was reduced in all three S. Infantis-challenged groups compared to the microbiome of mock-vaccinated/mock-challenged turkeys, although to a lesser extent in the BBS 866 group. Greater beta diversity (PERMANOVA) was observed between the mock-vaccinated/mock-challenged group compared to the two vaccinated groups than to the mock-vaccinated/S. Infantis-challenged group. Examination of the microbiome and significant population differences can reveal bacterial niches important to the response to S. Infantis and vaccination, thereby potentially identifying mechanisms to improve intervention strategies against Salmonella. Partial funding: US Poultry & Egg Association.