Generation and evaluation of Salmonella entericaserovar Choleraesuis mutant strains as a potential live-attenuated vaccine.

Background: Salmonella enterica serovar Choleraesuis (S. C) is a swine enteric pathogen causing paratyphoid fever, enterocolitis, and septicemia in piglets. S. C is mainly transmitted through the fecal-oral route. Vaccination is an effective strategy for preventing and controlling Salmonella infection. Results: Herein, we used CRISPR-Cas9 technology to knockout the virulence regulatory genes, rpoS, and slyA of S. C and constructed the ∆rpoS , ∆slyA, and ∆rpoS ∆slyA strains. The phenotypic characteristics of the mutant strains remained unchanged compared with the parental wild-type strain. In vivo study, unlike the wild-type strain, the ∆slyA and ∆rpoS ∆slyA strains alleviated splenomegaly, colon atrophy, and lower bacterial loads in the spleen, liver, ileum, and colon. These mutant strains survived in Peyer's patches (PPs) and mesenteric lymph nodes (MLN) for up to 15 days post-infection. Furthermore, the immunization of the ∆rpoS ∆slyA strain induced robust humoral and cellular immune responses. Conclusions: Consequently, vaccination with ∆rpoS ∆slyA conferred a high percentage of protection against lethal invasive Salmonella , specifically S. C , in mice. This study provided novel insights into the development of live-attenuated vaccines against the infection of S. C. • Three mutant Salmonella enterica serovar Choleraesuis (S. C) strains ∆rpoS , ∆slyA , and ∆rpoS ∆slyA were generated. • The mutant S.C. strains remained similar phenotypes with the parental strain but with much lower virulence. • The ∆rpoS ∆slyA S.C strain showed ideal immunity and protective efficacy. [ABSTRACT FROM AUTHOR]