Hubei Key Laboratory of Animal Nutrition and Feed Science, School of Animal Science and Nutritional Engineering, Wuhan Polytechnic University, Wuhan 430023, PR China.
Microb Pathog. 2011 Jul-Aug;51(1-2):69-76. doi: 10.1016/j.micpath.2010.10.001. Epub 2010 Nov 18.
Streptococcus suis serotype 2 is an important zoonotic pathogen that causes serious diseases such as meningitis, septicemia, endocarditis, arthritis and septic shock in pigs and humans. Little is known about the regulation of virulence gene expression in S. suis serotype 2. In this study, we cloned and deleted the entire tig gene from the chromosome of S. suis serotype 2 SC21 strain, and constructed a mutant strain (Δtig) and a complementation strain (CΔtig). The results demonstrated that the tig gene, encoding trigger factor from S. suis serotype 2 SC21, affects the stress tolerance and the expression of a few virulence genes of S. suis serotype 2. Deletion of the tig gene of S. suis serotype 2 resulted in mutant strain, ΔTig, which exhibited a significant decrease in adherence to cell line HEp-2, and lacked hemolytic activity. Tig deficiency diminishes stresses tolerance of S. suis serotype 2 such as survive thermal, oxidative and acid stresses. Quantification of expression levels of known S. suis serotype 2 SC21 virulence genes by real-time polymerase chain reaction in vitro revealed that trigger factor influences the expression of epf, cps, adh, rpob, fbps, hyl, sly, mrp and hrcA virulence-associated genes. ΔTig was shown to be attenuated in a LD50 assay and bacteriology, indicating that trigger factor plays an important part in the pathogenesis and stress tolerance of. S. suis serotype 2 infection. Mutant ΔTig was 100% defective in virulence in CD1 mice at up to 107 CFU, and provided 100% protection when challenged with 107 CFU of the SC21 strain.
猪链球菌 2 型是一种重要的人畜共患病病原体，可引起猪和人类严重疾病，如脑膜炎、败血症、心内膜炎、关节炎和感染性休克。目前对于猪链球菌 2 型毒力基因表达的调控机制知之甚少。本研究从猪链球菌 2 型 SC21 株染色体上克隆并缺失了整个 tig 基因，构建了突变株（Δtig）和互补株（CΔtig）。结果表明，tig 基因（编码猪链球菌 2 型 SC21 的触发因子）影响猪链球菌 2 型的应激耐受和一些毒力基因的表达。猪链球菌 2 型 tig 基因缺失导致突变株ΔTig 对细胞系 HEp-2 的黏附能力显著降低，且缺乏溶血活性。Tig 缺失降低了猪链球菌 2 型对热、氧化和酸应激的耐受能力。实时聚合酶链反应体外定量检测已知的猪链球菌 2 型 SC21 毒力基因的表达水平表明，触发因子影响 epf、cps、adh、rpob、fbps、hyl、sly、mrp 和 hrcA 等毒力相关基因的表达。LD50 试验和细菌学试验表明，ΔTig 株的毒力明显减弱，表明触发因子在猪链球菌 2 型感染的发病机制和应激耐受中发挥重要作用。在 CD1 小鼠中，突变株ΔTig 的毒力在高达 107 CFU 时完全丧失，用 107 CFU 的 SC21 株攻毒时可提供 100%的保护。
