2型猪链球菌N-乙酰半乳糖胺和半乳糖胺代谢通路中SSU0448基因功能的初步研究

发布时间：2018-10-12 07:28

【摘要】：猪链球菌(Streptococcus suis, S.suis)是一种重要的猪感染致病菌。根据其夹膜抗原的多样性可分为35个血清型。其中2型猪链球菌是致病性最强,临床检出率最高,分布范围最广的一种致病菌。2型猪链球菌(Streptococcus suis serotype 2,SS2)作为重要的人兽共患病病原菌,人被该病原菌感染后会患脑膜炎、心内膜炎、败血症、肺炎甚至导致急性死亡。1998年江苏南通和2005年四川资阳地区爆发了大规模的2型猪链球菌感染人事件。值得注意的是,这两次报道的2型猪链球菌感染人事件的临床表现为高侵袭率、深部组织感染以及中毒性休克综合症(streptococcus toxic shock syndrome, STSS)。全世界范围内,2型猪链球菌感染人的事件时有发生,然而其致病机制尚不清楚。通过生物信息学分析预测SSU0448基因是2型猪链球菌强毒株05ZYH33中参与N-乙酰半乳糖胺和半乳糖胺代谢的关键转录调控因子。本研究应用同源重组基因敲除的方法构建和筛选强毒株05ZYH33中SSU0448基因缺失的突变株Δ0448,和功能互补株CΔ0448,系统比较分析突变株Δ0448与野生株05ZYH33、功能互补株CA0448的基本生物学特性,以及SSU0448基因的缺失对N-乙酰半乳糖胺和半乳糖胺代谢通路中相关分子的转录改变情况,并通过小鼠毒力实验探索SSU0448基因缺失对2型猪链球菌毒力的影响。实验结果表明,突变株A0448对数生长期稍短且较快速到达平台期,在成链能力上较野生株明显减弱,而在菌落形态、革兰染色和溶血活性方面突变株与野生株、并无明显差异；小鼠毒力实验提示SSU0448基因缺失对2型猪链球菌的毒力并无显著改变,但可能延缓致病过程。综上所述,2型猪链球菌中缺失SSU0448基因会导致其生长加快,成链能力降低；在以小鼠为模型的致病实验中,可能延缓2型猪链球菌的致病过程,但不显著改变其对小鼠的侵袭致病能力,我们的研究结果为深入探索2型猪链球菌的致病感染机制提供了依据。
[Abstract]:Streptococcus suis (Streptococcus suis, S.suis) is an important pathogen of swine infection. It can be divided into 35 serotypes according to the diversity of membrane antigen. Streptococcus suis type 2 is one of the most pathogenic bacteria with the highest clinical detection rate and the most widespread distribution. As an important zoonotic pathogen, Streptococcus suis type 2 can be infected with meningitis. Endocarditis, septicemia, pneumonia even lead to acute death. In 1998 and 2005, there were massive human events of Streptococcus suis type 2 infection in Nantong, Jiangsu Province and Ziyang, Sichuan Province. It is worth noting that the two reported human events of Streptococcus suis type 2 were characterized by high invasive rates, deep tissue infections and toxic shock syndrome (streptococcus toxic shock syndrome, STSS). Human infection of Streptococcus suis type 2 occurs from time to time around the world, but its pathogenetic mechanism is unclear. It was predicted by bioinformatics that SSU0448 gene was the key transcription regulator in the metabolism of N-acetylgalactosamine and galactosamine in 05ZYH33, a virulent strain of Streptococcus suis type 2. In this study, the homologous recombinant gene knockout method was used to construct and screen SSU0448 gene deletion mutant 螖 0448 and functional complementary strain C 螖 0448 in 05ZYH33. The basic biological characteristics of mutant 螖 0448 and wild strain 05ZYH33 and functional complementary strain CA0448 were systematically analyzed. The transcriptional changes of related molecules in N-acetylgalactosamine and galactosamine metabolism pathway were also investigated by SSU0448 gene deletion. The virulence of SSU0448 gene deletion on Streptococcus suis type 2 was investigated by virulence test in mice. The results showed that the logarithmic growth period of mutant A0448 was shorter than that of wild strain, and the ability of chain formation was weaker than that of wild strain, but there was no significant difference between mutant strain and wild strain in colony morphology, Gram staining and hemolytic activity. The virulence test showed that the SSU0448 gene deletion did not change virulence of Streptococcus suis type 2, but it might delay the pathogenicity. In conclusion, the deletion of SSU0448 gene in Streptococcus suis type 2 may lead to faster growth and lower chain forming ability, which may delay the pathogenicity of Streptococcus suis type 2 in mice. But it did not change the ability of invasiveness and pathogenicity in mice. Our results provided a basis for further exploring the pathogenic mechanism of Streptococcus suis type 2.
【学位授予单位】：南京师范大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：S852.611

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