The Role of SaeR/S During Staphylococcus aureus Skin Infections

描述（由申请人提供）：金黄色葡萄球菌（S. aureus）是人类发病和死亡的主要原因。被归类为脉冲场凝胶电泳型（PFGE） USA300的菌株特别擅长引起皮肤和软组织感染。最近的一份报告确定耐甲氧西林金黄色葡萄球菌（MRSA）是美国急诊室感染的主要原因，占皮肤和软组织感染的59%。社区相关的MRSA菌株USA300被确定为这些感染的97%的病原体。本提案的目的是追求金黄色葡萄球菌在宿主-病原体界面使用的特定分子机制。由于社区相关的mrsa菌株USA300是皮肤感染的主要原因，我们使用小鼠皮肤和软组织感染模型研究了SaeR/S双组分基因调控系统在该菌株中的作用。USA300的saeR/S等基因缺失突变体(USA300？saeR/S)与USA300相比，感染的发生率和严重程度显著降低。体外寡核苷酸芯片和实时逆转录酶聚合酶链式反应检测鉴定了USA300？saeR/S和在毒力基因启动子内直接结合重组saeR的一致序列。在宿主方面，我们已经确定SaeR/ s影响因子改变了局部促炎细胞因子IFN的产生。和肿瘤坏死因子?在软组织感染期间。基于初步数据，我们假设SaeR/S直接影响的毒力因子调节金黄色葡萄球菌皮肤感染的严重程度。我们将用两个具体目标来检验这一假设。在特异性目标1中，我们将确定SaeR是否在皮肤感染期间直接调节金黄色葡萄球菌的体内毒力基因。saeR/ s调控的毒力因子的具体作用将通过创建等基因突变体和研究它们对葡萄球菌发病机制的影响来追求。在特异性目标2中，我们将通过检验SaeR/ s调节因子降低TNF？增加干扰素？促进葡萄球菌皮肤感染的发病机制。总的来说，这项研究将通过确定促进皮肤感染的特定金黄色葡萄球菌因子，提高我们对初始宿主-病原体相互作用的理解，并可能对使用免疫调节疗法治疗金黄色葡萄球菌感染有潜在的影响。鉴于我们目前抗生素的有效性正在下降，很明显，我们必须提高对金黄色葡萄球菌毒力的基本分子机制的理解，以控制这种可能危及生命的病原体引起的疾病。

DESCRIPTION (provided by applicant): Staphylococcus aureus (S. aureus) is a major cause of human morbidity and mortality. Strains classified as pulsed-field gel electrophoresis type (PFGE) USA300 are particularly adept at causing skin and soft-tissue infections. A recent report identified methicillin-resistant S. aureus (MRSA) as the leading cause of infections presenting to emergency departments across the United States accounting for ~ 59% of skin and soft-tissue infections. Community-associated MRSA strain USA300 was identified as the causative agent in e 97% of these infections. The objective of this proposal is to pursue specific molecular mechanisms used by S. aureus at the host-pathogen interface. As community associated-MRSA strain USA300 is a major cause of skin infections, we examined the role of the SaeR/S two-component gene regulatory system in this strain using a murine model of skin and soft-tissue infection. A saeR/S isogenic deletion mutant of USA300 (USA300?saeR/S) demonstrated a significant decrease in incidence and severity of infection compared to USA300. In vitro oligonucleotide microarray and real-time reverse-transcriptase polymerase chain reaction assays identified numerous extracellular virulence genes down-regulated in USA300?saeR/S and direct binding of recombinant SaeR to a consensus sequence within virulence gene promoters. On the host side, we have determined that SaeR/S-influenced factors alter the local production of pro-inflammatory cytokines IFN? and TNF? during soft-tissue infections. Based on preliminary data, we hypothesize that virulence factors under the direct influence of SaeR/S modulate the severity of S. aureus skin infections. We will test this hypothesis with two specific aims. In Specific Aim 1 we will determine if SaeR directly regulates S. aureus virulence genes in vivo during skin infection. Specific roles of saeR/S-regulated virulence factors will be pursued by creating isogenic mutants and investigating their influence on staphylococcal pathogenesis. In Specific Aim 2, we will define the SaeR/S-specific host response by testing the hypothesis that SaeR/S-regulated factors decrease TNF? and increase IFN? to promote pathogenesis during staphylococcal skin infection. Collectively, this research will improve our understanding of the initial host-pathogen interactions by identifying specific S. aureus factors that promote skin infection and may potentially have implications for the use of immunomodulatory therapy to treat S. aureus infections. Given the diminishing effectiveness of our current antibiotics, it is clear we must improve understanding of molecular mechanisms fundamental to S. aureus virulence to control disease caused by this potentially life-threatening pathogen. PUBLIC HEALTH RELEVANCE: Staphylcoccus aureus (S. aureus) is a leading cause of morbidity and mortality worldwide. The emergence of hyper-infectious community-associated methicillin resistant (CA-MRSA) strains within the community is a major public health concern. Given the diminishing effectiveness of our current antibiotics, it is clear we must improve our understanding of molecular mechanisms fundamental to S. aureus pathogenesis in order to develop better methods to control/treat CA-MRSA disease and thus improve public health.