Proline uptake in staphylococcus aureus pathogenesis

金黄色葡萄球菌是一种重要的人类病原体，它是外科伤口感染的主要原因，也是美国医院血液感染的第二大常见原因。相当数量的食物中毒病例也与金黄色葡萄球菌污染食品有关。几乎人体内的每一个组织和器官都容易受到这种细菌的感染。目前的许多感染是由对一种或多种抗生素具有耐药性的葡萄球菌菌株引起的。所有金黄色葡萄球菌菌株中有80%至90%对抗生素青霉素具有耐药性，从医院病人身上分离出的所有菌株中有多达50%对甲氧西林具有耐药性。最近爆发的具有甲氧西林耐药性的社区获得性金黄色葡萄球菌和耐万古霉素金黄色葡萄球菌菌株的出现意味着一些菌株可能无法用任何抗生素治疗。由于金黄色葡萄球菌能够感染人体内如此多的不同组织，因此本基金建议研究金黄色葡萄球菌中的脯氨酸转运，作为研究脯氨酸转运蛋白在细菌发病机制中所起作用的手段。已知金黄色葡萄球菌至少有两种脯氨酸运输系统。本项目拟鉴定低亲和脯氨酸转运蛋白ProP的同源物，并与Tn917通过等位基因交换或转座子诱变使ProP基因突变。有了这个proP突变体，就会创建一个proptp双突变体。将测试单突变体和双突变体在体外的脯氨酸转运差异以及它们在感染动物模型中的衰减。高亲和脯氨酸转运基因putP的调控也将在体外进行脯氨酸摄取试验，并在几种动物感染模型中使用putP转录融合进行体内试验。本研究的结果将有助于我们了解脯氨酸转运在金黄色葡萄球菌感染中的作用。

Staphylococcus aureus is a significant human pathogen, which is the leading cause of surgical-wound infections and the second most frequent cause of nosocomial bloodstream infections in the United States. A significant number of cases of food poisoning are also linked to contamination of foodstuffs with S. aureus. Almost every tissue and organ within the human body is susceptible to infections by this species. Many of the current infections are caused by staphylococcal strains that are resistant to one or more antibiotics. Eighty to ninety percent of all S. aureus strains are resistant to the antibiotic penicillin and up to fifty percent of all strains isolated from patients in hospitals are resistant to methicillin. Recent outbreaks of community-acquired S. aureus possessing methicillin resistance and the emergence of vancomycin-resistant S. aureus strains mean that some strains may be untreatable by any antibiotic. Because S. aureus is able to infect so many different tissues within the human body, this grant proposes to study proline transport in S. aureus as a means to study the role proline transporters play in the pathogenesis of the bacteria. At least two proline transport systems are known for S. aureus. This grant proposes to identify the homolog of the ProP low affinity proline transporter and mutate the prop gene by allelic exchange or transposon mutagenesis with Tn917. With this proP mutant, a proPputP double mutant will then be created. Both the single and double mutants will be tested for proline transport differences in vitro and for their attenuation in animal models of infection. The regulation of the high affinity proline transport gene, putP, also will be tested in vitro in proline uptake assays and in vivo in several animal models of infection using a putP transcriptional fusion. The results of this study will help us understand the role of proline transport in S. aureus infections.