Characterization and immunoprotection of thioredoxin reductase TrxB knockout mutant of Salmonella Enteritidis

Background Salmonella Enteritidis ( S . Enteritidis) is an important zoonotic pathogen that poses a major threat to animals and human health. TrxB, as a key component of the thioredoxin system, is a thioredoxin reductase ubiquitously present in organisms. It is mainly involved in maintaining cellular redox balance, but its role in the pathogenicity of S . Enteritidis remains unclear. Methods In this study, we generated a trxB -deficient strain from S . Enteritidis C50336 strain to investigate how TrxB affects the biological characteristics and pathogenesis of the bacterium. The virulence of Δ trxB was assessed by measuring Δ trxB resistance to environmental stress, biofilm formation ability, motility, adhesion, invasion ability, intracellular survival, LD 50 , virulence gene expression levels, and in vivo colonization ability. Additionally, the study measured specific IgG antibody levels in mice, lymphocyte proliferation, and the immunoprotective effect of Δ trxB . Results We found that deletion of trxB gene did not affect the growth and biochemical properties of the S . Enteritidis strain but significantly reduced its motility, drug resistance, biofilm formation, and tolerance to environmental stress. After trxB knocked out, the adhesion and invasion capacities of S . Enteritidis to Caco-2 cells, along with its proliferation in RAW264.7 cells, were significantly reduced. Additionally, the trxB -deficient strain exhibited significantly lower pathogenicity than the parental strain, evidenced by a more than 100-fold increase in LD 50 . We also observed a significant decrease in the expression of virulence-related genes in the trxB -knockout mutant. More importantly, immunization with this deletion strain can confer promising protection against challenge with the C50336 strain. Conclusion These findings indicate that TrxB is a crucial virulence factor in S . Enteritidis, playing critical roles in its pathogenicity.