Chicken vaccination reduces colonization and dissemination of Salmonella serovar Enteritidis with decreased susceptibility to ciprofloxacin

Salmonella enterica serovar Enteritidis (S. Enteritidis) is one of most common Salmonella serovars associated with human illness in the U.S. and worldwide. Surveillance from the U.S. National Antimicrobial Resistance Monitoring System indicates an increase in both chicken and human isolates of S. Enteritidis with decreased susceptibility to ciprofloxacin (DSC), a critical antibiotic prescribed for complicated human salmonellosis infections. S. Enteritidis reduction in chickens is a priority of poultry producers and public health agencies to improve food safety. In the current study, efficacy assessment of a live Salmonella vaccine (BBS 1134) revealed significant reduction of cecal and splenic colonization, and prevention of dissemination to the bone marrow by DSC S. Enteritidis in broiler chickens. Microbiome analysis indicated the cecal microbiota of vaccinated chickens is distinct compared to mock-vaccinated birds. The IDEXX SE Ab X2 Test did not detect antibodies to S. Enteritidis in vaccinated chicken serum, thereby permitting differentiation of infected from vaccinated animals (DIVA). Altogether, the Salmonella vaccine is a DIVA vaccine, afforded cross-protection, and significantly reduced intestinal colonization and dissemination to the spleen and bone marrow by DSC S. Enteritidis in chickens, thereby offering a prospective intervention for animal production to reduce food product contamination and improve food safety.