Virulence and oxidative stress in Streptococcus pneumoniae

肺炎链球菌是一种重要的人类病原体，可引起肺炎、脑膜炎、菌血症以及幼儿中耳炎。它是全世界发病率和死亡率高的原因。S.肺炎通过厌氧生物体的特征发酵代谢生长，但它能够适应环境中的氧气。这种适应能力使S.肺炎在高氧张力条件下生存（例如，上呼吸道）或在几乎无氧的条件下（例如，中耳）。抗生素耐药肺炎球菌的出现和目前疫苗的局限性导致人们对了解这种细菌发病机制的分子机制越来越感兴趣。特别令人感兴趣的是肺炎球菌表面抗原PsaA，它已被证明是小鼠的保护性免疫原。还已经表明，psaA突变体在小鼠鼻内和腹膜内攻击模型中表现出大规模降低的毒力。总之，这些数据表明PsaA可能是有效的疫苗抗原或抗微生物靶标。我们假设PsaA参与有氧条件下的氧化应激反应和毒力，并设计了一项研究，以确定这种蛋白质在肺炎链球菌引起的疾病中的作用。

Streptococcus pneumoniae is an important human pathogen that causes pneumonia, meningitis and bacteraemia as well as otitis media in young children. It is a cause of high morbidity and mortality around the world. S. pneumoniae grows by fermentative metabolism, a characteristic of anaerobic organisms, but it is able to adapt towards oxygen in the environment. This adaptive ability enables S. pneumoniae to live under conditions of high oxygen tension (eg. the upper respiratory tract) or under almost anaerobic conditions (eg. the middle ear) in the human body. The emergence of antibiotic resistant pneumococci and limitations of current vaccines has led to increased interest in understanding the molecular mechanisms of pathogenesis of this bacterium. Of particular interest has been the pneumococcal surface antigen PsaA, which has been shown to be a protective immunogen in mice. It has also been shown that psaA mutants exhibit massively reduced virulence in mice in intranasal and intraperitoneal challenge models. Taken together, these data have led to the suggestion that PsaA might be an effective vaccine antigen or antimicrobial target. We postulate that PsaA is involved in the oxidative stress response and virulence under aerobic conditions and have devised a study to determine the procise role of this protein in disease caused by Streptococcus pneumoniae.