金黄色葡萄球菌(金葡菌)是一种重要的食源性致病菌。本课题组前期研究表明众多金葡菌引起的食物中毒事件与ST6型金葡菌表达一种新的肠毒素SEE2密切相关。为阐明肠毒素SEE2的特性及其毒性机制，本课题以原核表达SEE2蛋白为材料，采用Western blot方法、体外淋巴细胞增殖试验、体外耐消化酶及耐热性试验、小鼠致死试验和和幼猫呕吐试验，确证SEE2蛋白的肠毒素特征及生物活性；通过构建sea和see2单基因或双基因敲除ST6型菌株，对比分析sea和see2基因敲除前后细菌培养上清液对小鼠致死率及幼猫催吐能力的差异，阐明see2基因对ST6型金葡菌致病性的影响。本研究将揭示新的肠毒素SEE2在ST6型金葡菌引发食物中毒方面的作用机制，为金葡菌引起的食物中毒的防控提供理论依据。

Staphylococcus aureus (S. aureus) is an important foodborne pathogen. Our preliminary experiments have shown that a novel enterotoxin SEE2 is commonly associated with many foodborne outbreaks caused by S. aureus ST6. The aim of this proposal is to elucidate the characteristics and toxicity mechanism of SEE2. SEE2 will be obtained from an expressing vector containing see2 gene. The characteristics and biological activity of SEE2 will be determined by Western blot, lymphocyte proliferation test, digesting enzyme tolerance test, heat stability test, mouse lethality test and kitten emesis test. After constructing sea and see2 single gene and double genes knockout in S. aureus ST6 strains, the toxicity of culture supernatant of each mutant strain was compared with control strain by testing the mortality of mice and the frequency and severity of emesis in kitten. These findings will clarify the role of SEE2 in the pathogenesis of S. aureus ST6 and mechanism of action of SEE2 in staphylococcal food poisoning, which will provide theoretic basis for prevention and control of illness caused by S. aureus.