中文摘要：

猪链球菌（Streptococcus suis,SS）是一种重要的人畜共患病原菌,在33个血清型中,2型（SS2）毒力最强、分布最广,但其具体的致病机理尚不完全清楚。前期的比较基因组学研究表明,RTX family exoprotein A gene（rfeA）只存在于强毒菌株中,基因生物信息学分析发现rfeA与epf-like位于同一操纵子上,且与传统毒力因子ef邻近,PCR方法检测表明teA在猪链球菌2型中分布广泛。为了研究rfeA的致病机制,利用同源重组构建了rfeA的基因缺失株ΔrfeA和互补株CΔrfeA,并通过斑马鱼模型对缺失株、互补株和野生株的毒力进行评估,发现缺失株毒力增强,表明rfeA可能是SS2的一个新调控因子,或者可能影响其他调控因子。

英文摘要：

Streptococcus suis,SS is an important zoonotic pathogen causing a variety of diseases. In all 33 serotypes described,S. suis serotype 2（ SS2） is the most invasive and prevalent serotype. However,little is known about its precise pathogenesis. A gene belonging to RTX family exoprotein,rfe A,was only detected in virulent strains of SS2 and located in the same operon of epf-like gene by comparsion with the avirulent counterparts. Further gene distribution detection among different strains of S. suis showed that it was common in the virulent isolates of SS2. To investigate the pathogenic mechanism of Rfe A in SS2,an isogenic mutant strain（ Δrfe A） and the functionally complementation strain（ CΔrfe A） were constructed. Then the virulence of Δrfe A,CΔrfe A,and wild type strain were evaluated in zebrafish. Compared with the wild strain,the virulence of Δrfe A was significantly enhanced,while CΔrfe A had relatively low virulence. It suggests that Rfe A might be a novel negative regulatory factor in SS2,or on the other hand,it might affect other negative regulatory factors.