Identification and characterisation a surface-associated arginine peptidase in Streptococcus suis serotype 2.

ABSTRACT

Streptococcus suis is an important zoonotic pathogen worldwide and is responsible for disease in swine and humans. In the present study, we identified and characterised a surface-associated peptidase (abpb, amylase-binding protein B) in Streptococcus suis serotype 2 (S. suis 2) that has high hydrolytic activity towards H-Arg-pNa, with maximum activity at pH 7.0. Stimulation of RAW 264.7 macrophages with purified recombinant abpb protein triggered the release of pro-inflammatory cytokines. An abpb-deficient mutant ΔAbpb was constructed by homologous recombination to determine the role of abpb in S. suis 2. The mutant ΔAbpb showed decreased adherence to Hep-2 cells and attenuated virulence in a mouse model compared to the wild type strains. The results of the infection showed impaired bacterial growth in vivo and poor colonisation of the organs. In a protection assay, the recombinant abpb provided excellent protection against a lethal challenge of S. suis 2. Together, these findings suggest that abpb contributes to the pathogenicity of S. suis 2 and may be another target for S. suis prevention and control.