The cation-uptake regulators AdcR and Fur are necessary for full virulence of Streptococcus suis

In streptococci, the pleiotropic regulators AdcR and Fur control the transport of, zinc and iron, respectively, which are essential components of many proteins. In this work, ΔadcR, Δfur, and ΔadcR Δfur mutants of Streptococcus suis, a serious pathogen in pigs and humans, were assayed in a mouse model to determine their involvement in the virulence of this bacterium. The results showed, for the first time, that the virulence of S. suis mutants carrying an inactivation of adcR, fur, or both genes is significantly attenuated compared to the wild-type parent strain. Furthermore, all mutants were found to be more sensitive to oxidative stress. Our data provide evidence that the adcR and fur genes play important roles in the oxidative stress response of S. suis as well as in the full virulence of this bacterium.