Oral live bivalent Salmonella vaccine reduces clinical disease, colonization and fecal shedding of multidrug resistant Salmonella enterica serovar I 4,[5],12:i:-

Salmonella enterica serovar I 4,[5],12:i:- is currently the most common serovar identified in U.S. swine clinical cases and is prevalent worldwide. This serovar also ranks among the leading causes of human foodborne salmonellosis and is the most frequently identified multidrug-resistant (MDR; resistance to ≥3 antimicrobial classes) Salmonella serovar in the U.S. Given its importance to both swine health and food safety, the current study evaluated the efficacy of a commercial vaccine containing live attenuated Salmonella enterica serovars Typhimurium and Choleraesuis in pigs challenged with MDR Salmonella I 4,[5],12:i:-. Pigs vaccinated with a single oral dose exhibited significantly reduced diarrhea and lower body temperatures following challenge compared to non-vaccinated pigs (n = 20/group). During the 14-days post-challenge, vaccinated pigs also demonstrated significantly reduced fecal shedding and up to a 2.3-log reduction in intestinal tissue colonization, as well as a significant reduction in the number of pigs colonized, compared to non-vaccinated pigs. Furthermore, weight gain was significantly higher in vaccinated pigs compared to non-vaccinated pigs after challenge. Collectively, these results demonstrate that vaccination significantly reduces clinical disease, fecal shedding, and tissue colonization following challenge with MDR Salmonella I 4,[5],12:i:-, revealing the vaccine to be an effective pre-harvest tool to improve both animal health and food safety.