Lexin Zhu Mengqing Li Guijun Yu Dongbo Zhan Wenzhen Zeng Nanyan Fu xiaowu Jiang ^*

• Yichun University, Yichun, China

Streptococcus suis serotype 2 (S. suis type 2, SS2) is one of the zoonotic pathogens known to induce meningitis, septicemia, and arthritis in both pigs and human, resulting in public health concern. CbpD, also termed as CrfP, is one of the Choline-binding proteins (CBPs) which was found as a murein hydrolase in SS2 and play crucial roles in natural genetic transformation under the control of ComRS-ComX regulatory system by a previous study. Nonetheless, the possible functions of CbpD in virulence and pathogenesis in SS2 remain unclear. In this study, a cbpD gene mutant (ΔcbpD) with its complemental strain (cΔcbpD) was constructed and further used to examining pathogenic roles of CbpD in SS2 infection. The results showed that the cbpD deficiency lead to increased bacterial chains elongation and aggregation with little impact on growth capability of SS2. The ΔcbpD strain represented more vulnerable to a thermo, acid or oxidative stress. Elevated adhesion to human epithelial HEp-2 cells, decreased invasion into bEND3.0 cells and more easily to be phagocytosed by murine RAW264.7 macrophages of ΔcbpD were found.The virulence of cbpD mutant was attenuated in a mouse infection model. Enhanced susceptibility within mice blood, impaired ability to colonize organs with alleviated histopathological lesions were also demonstrated as compared with wild type of SS2.It is noteworthy that the discrepant expression of multiple virulence-associated factors including serine/threonine phosphorylase Stp, anti-phagocytosis factor of transglutaminase TGase and adhesin of chaperon DnaJ, were examined resulting from the deletion of cbpD. Overall, these findings provided evidence that the CbpD factor contributes to SS2 infection and involved in bacterial adhesion, invasion and anti-phagocytosis process by modulating crucial virulence associated factors expression.