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

Authors: LEITE, FERNANDO - Boehringer Ingelheim; ARRUDA, PAULO - Vri; FORD, BRIANNA - Boehringer Ingelheim; JORDAN, DIANNA - Boehringer Ingelheim; GIMENEZ-LIROLA, LUIS - Iowa State University; MORA-DIAZ, JUAN CARLOS - Iowa State University; BRADSHAW, DAVID - Oak Ridge Institute For Science And Education (ORISE); Bearson, Shawn

Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/18/2025
Publication Date: 7/26/2025
Citation: Leite, F.L., Arruda, P., Ford, B., Jordan, D., Gimenez-Lirola, L., Mora-Diaz, J., Bradshaw, D., Bearson, S.M. 2025. Oral live bivalent Salmonella vaccine reduces clinical disease, colonization and fecal shedding of multidrug resistant Salmonella enterica serovar I 4,[5],12:i:-. Vaccine. 62. Article 127540. https://doi.org/10.1016/j.vaccine.2025.127540.
DOI: https://doi.org/10.1016/j.vaccine.2025.127540

Interpretive Summary: Salmonella infections pose a significant threat to both human and animal health. Salmonella enterica serovar I 4,[5],12:i:- has emerged as the predominant serovar in swine clinical samples in the United States, with its increasing prevalence in swine closely correlating with rising detection in human surveillance data. Analysis of five U.S. surveillance systems revealed that 63% of multidrug resistant (MDR) Salmonella I 4,[5],12:i:- outbreaks were associated with pork consumption or swine contact, highlighting the need for mitigation strategies to reduce carriage in swine to protect human health. The current study assessed the efficacy of a commercial vaccine in reducing clinical disease parameters, colonization, and fecal shedding of Salmonella I 4,[5],12:i:- in swine. The results demonstrate that vaccination significantly improved weight gain of pigs and reduced both fecal shedding and colonization of various tissues in pigs with Salmonella I 4,[5],12:i:-, thereby demonstrating the effectiveness of the vaccine as an intervention to enhance swine health and improve food safety.

Technical Abstract: 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. The serovar is also one of the most common causes of human foodborne salmonellosis and the most frequent multidrug resistant (MDR; resistance to = 3 antimicrobial classes) serovar in the U.S. Given the significance of this serovar to both swine health and food safety, the present study evaluated the impact of a commercial vaccine containing live attenuated strains of Salmonella enterica serovars Typhimurium and Choleraesuis in swine experimentally challenged with MDR Salmonella I 4,[5],12:i:-. Pigs vaccinated with a single oral dose exhibited a significant reduction in diarrhea and fever following challenge with MDR Salmonella I 4,[5],12:i:- compared to non-vaccinated pigs (n=20/group). During the 14-day period following challenge, a significant reduction in Salmonella fecal shedding was observed in the vaccinated pigs, and vaccination yielded up to a 2.3-log reduction in colonization of intestinal tissues, as well as a significant reduction in the number of pigs colonized, compared to the non-vaccinated pigs. Furthermore, weight gain was significantly higher in the vaccinated pigs compared to mock-vaccinated pigs following challenge with MDR Salmonella I 4,[5],12:i:-. Collectively, the data demonstrated significant reduction in clinical disease, tissue colonization and fecal shedding of MDR Salmonella I 4,[5],12:i:- in vaccinated pigs, revealing the vaccine to be an effective pre-harvest tool to improve animal health and food safety.