Construction and characterization of ssrAB, hilA, hilD-deficient mutants of Salmonella enteritidis

Abstract:

[Background] Salmonella is an important zoonotic pathogen, due to the continuous emergence of drug-resistant strains, research on new prevention methods is imminent. [Objective] In order to investigate the effect of ssrAB, hilA, hilD genes on the pathogenicity of Salmonella enteritidis and screen safe and reliable strains for Salmonella live attenuated vaccines or vectors. [Methods] Using suicide plasmid-mediated homologous recombination technology to construct the single (ΔssrAB, ΔhilA, ΔhilD), double (ΔssrABhilA, ΔssrABhilD, ΔhilAhilD) and triple (ΔssrABhilAhilD) gene deletion strains, then comparing the differences in biological characteristics between the above-mentioned deletion strains and the parent strain. [Results] The growth rate of the mutant strains was not significantly different from the parent strains (P>0.05). The biofilm formation ability of ΔhilD was the strongest, and the other gene deletion strains had no significant changes (P>0.05). The LD50 of ΔssrABhilAhilD and ΔssrABhilA were the highest, ΔssrAB, ΔhilA and ΔhilD were the second, and the degree of duodenal lesions in mice caused by the parent strain is significantly more serious than deleted strains. Among all the deleted strains, the adhesion of ΔssrABhilAhilD to HeLa cells was the lowest, while the colonization rate of ΔhilD in mice was the highest. Besides, the body’s ability to secrete IL-1, IL-18 and IFN-γ has no significant correlation with ssrAB, hilA and hilD genes of Salmonella (P>0.05). [Conclusion] Among the 7 gene deletion strains constructed in this study, ΔssrAB, ΔhilA, ΔhilD, ΔssrABhilA and ΔssrABhilAhilD had the characteristics of low pathogenicity, well growth rate, and they could effectively stimulate cytokine production, which had the potential to be Salmonella live attenuated vaccines or vectors.