Adhesion and Invasion of Streptococcus suis Type 2 to Tonsil Epithelial Cells from Neonatal Rabbit
猪链球菌2型对扁桃腺上皮细胞的黏附和侵袭作用

Streptococcus suis type 2 (SS2) is one of the most important zoonotic pathogens world wide. Muramidase released protein (MRP) is a key virulence factor of SS2. In this paper, both SS2 strains, HA9801, naturally with MRP expression, isolated from Jiangsu province and SH006444, without MRP, from Shanghai, were used to study adhesion and invasion of SS2 to tonsil epithelial cells from neonatal rabbit. Adhesion counting assay demonstrated high adhesive levels of both strains. Scanning and transmission electron microscope observation further showed a dense adhering of HA9801 at cellular membrane and microvilli, and HA9801 cells were being internalized by the cell membrane. Lysis counting assay revealed a weak invasion of HA9801 and no invasion of SH006444 to tonsil epithelial cells from neonatal rabbit. Findings of this study suggested, firstly, the tonsil served as the colonizing site and an entrance of SS2 in establishment of infection; secondly, the direct invasion into epithelial cells following their adhesion was one of their mechanisms of breaking through the tonsil epithelial cell barrier.