Si Youhui, Yuan Fangyan, Chang Haitao, Liu Xijian, Li Hongru, Cai Kai, Xu Zhuofei, Huang Qinfeng, Bei Weicheng, Chen Huanchun
Division of Animal Infectious Disease, State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, Hubei, China.
Vet Microbiol. 2009 Oct 20;139(1-2):80-8. doi: 10.1016/j.vetmic.2009.04.024. Epub 2009 Apr 22.
Streptococcus suis serotype 2 (S. suis 2) is an important pathogen, responsible for diverse diseases in swine and human. In this study, we investigated the role of the glutamine synthetase (GlnA) in the pathogenesis of S. suis 2 in mice. To assess the contribution of glutamine synthetase (GlnA) to the virulence of S. suis 2, an knockout mutant (DeltaglnA) unable to produce GlnA was constructed, and the virulence level of wild-type (WT) SC19 and the DeltaglnA mutant strain were compared in an in vitro adherence assay and murine infection models. The data showed that DeltaglnA mutant exhibited a significant decrease in adherence to the epithelial cells HEp-2. The DeltaglnA mutant strain was attenuated and could reduce mortality and morbidity in murine infection models. Furthermore, organ cultures showed that GlnA plays a role in the colonization of the specific organs involved in S. suis infection. Functional complementation of the glnA gene into the knockout mutant DeltaglnA or incubated with extracellular glutamine restored its ability to adhere to the epithelial cells HEp-2. These findings suggested that glnA is required for the full virulence in S. suis 2. Therefore, the DeltaglnA mutant was considered as an attenuated mutant.
猪链球菌2型（S. suis 2）是一种重要的病原体，可导致猪和人类的多种疾病。在本研究中，我们调查了谷氨酰胺合成酶（GlnA）在S. suis 2感染小鼠发病机制中的作用。为了评估谷氨酰胺合成酶（GlnA）对S. suis 2毒力的贡献，构建了一个无法产生GlnA的基因敲除突变体（DeltaglnA），并在体外黏附试验和小鼠感染模型中比较了野生型（WT）SC19和DeltaglnA突变株的毒力水平。数据显示，DeltaglnA突变体对上皮细胞HEp-2的黏附能力显著下降。DeltaglnA突变株的毒力减弱，可降低小鼠感染模型中的死亡率和发病率。此外，器官培养表明GlnA在S. suis感染相关特定器官的定植中发挥作用。将glnA基因功能互补导入敲除突变体DeltaglnA或与细胞外谷氨酰胺孵育可恢复其对上皮细胞HEp-2的黏附能力。这些发现表明glnA是S. suis 2完全毒力所必需的。因此，DeltaglnA突变体被认为是一种减毒突变体。
