Virulence and oxidative stress in Streptococcus pneumoniae

肺炎链球菌是一种重要的人类病原体，可引起婴幼儿肺炎、脑膜炎、菌血症以及中耳炎。它是世界各地高发病率和高死亡率的原因之一。肺炎链球菌通过发酵代谢生长，这是厌氧生物的一个特征，但它能够适应环境中的氧气。这种适应能力使肺炎链球菌能够在高氧压条件下生存(例如。上呼吸道)或在几乎厌氧的条件下(例如。中耳)在人体内。耐药肺炎球菌的出现和现有疫苗的局限性使人们对了解这种细菌发病的分子机制产生了越来越大的兴趣。尤其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。研究还表明，psaA突变体在小鼠鼻腔和腹膜攻击模型中的毒力显著降低。综上所述，这些数据导致了PsaA可能是一个有效的疫苗抗原或抗菌靶点的建议。我们推测PsaA参与了有氧条件下的氧化应激反应和毒力，并设计了一项研究，以确定该蛋白在肺炎链球菌引起的疾病中的处理作用。

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.