Characterization studies on the 05SSU0969 gene of Streptococcus suis serotype 2 in adhesion, anti-phagocytosis, and virulence in animal.

Abstract

OBJECTIVE: Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen, however, the pathogenesis of SS2 remains unclear. Our objective was to study the role of the type IV secretion system (T4SS) 05SSU0969 gene in SS2 virulence. METHODS: To assess the function of 05SSU0969 in SS2 virulence, the wild-type strain 05ZYH33 served as the parent strain. Using homologous recombination technology, the mutant strain Δ0969 and the complemented strain CΔ0969 were generated. The biological properties of these strains were evaluated through growth curve analysis, cultivation characteristics, cell adhesion assays, blood survival assays, and pathogenicity tests in CD1 mice and piglets. RESULTS: Growth curve analysis revealed no significant differences among 05ZYH33, Δ0969, and CΔ0969. Although Δ0969 exhibited similar cultivation characteristics to 05ZYH33 on sheep blood agar, its adhesion to A549, Hep-2, and HBMEC cells was significantly impaired. Additionally, Δ0969 demonstrated markedly reduced blood survival and attenuated virulence in both mice and piglets models. CONCLUSIONS: These findings indicate that deletion of 05SSU0969 gene attenuates SS2 resistance and virulence in CD1 mice and piglets. However, the precise mechanism by which 05SSU0969 gene influences adhesion to A549, Hep-2, and HBMEC cells requires further investigation.