The role of glutathione for oxidative stress and pathogenicity of Streptococcus suis

Streptococcus suis is an important zoonotic pathogen that threatens human and pig health. During infection, the host can impose oxidative stress to resist pathogen invasion. Resistance to oxidative toxicity is an important factor for pathogens. Glutathione synthesis contributes to reactive oxygen species (ROS) detoxification in bacterial cells. Little is known about the roles of glutathione synthesis and transport in S. suis. In this study, we demonstrated that glutathione treatment increased oxidative stress tolerance in S. suis. GshAB and GshT were found in S. suis glutathione synthesis and import by bioinformatics. In vitro, inactivation of gshAB and gshT led to increased sensitivity to oxidative stress. Inactivation of gshT led to growth defects in the medium. The intracellular glutathione content of gshAB or gshT deletion mutants was lower than that of wild type (WT) strain. The phagocytic resistance of gshAB and gshT mutants was lower than that of the WT strain. Moreover, the virulence of gshAB and gshT deletion mutants was significantly lower than that of the WT strain in mouse survival and tissue loading experiments. In conclusion, these results revealed the functions of GshAB and GshT in the pathogenesis of S. suis. These findings enhance our understanding of bacterial virulence mechanisms and may provide a new avenue for therapeutic intervention aimed at curbing S. suis infections.