The Role of SaeR/S During Staphylococcus aureus Skin Infections

性状（由申请人提供）：金黄色葡萄球菌（S.金黄色葡萄球菌）是人类发病和死亡的主要原因。分类为脉冲场凝胶电泳型（PFGE）USA 300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了耐甲氧西林的S。金黄色葡萄球菌（MRSA）是美国急诊科感染的主要原因，占皮肤和软组织感染的约59%。社区相关的MRSA菌株USA 300被确定为这些感染中97%的病原体。本研究的目的是探讨S.金黄色葡萄球菌在宿主-病原体界面。由于社区相关MRSA菌株USA 300是皮肤感染的主要原因，我们使用皮肤和软组织感染的小鼠模型研究了SaeR/S双组分基因调控系统在该菌株中的作用。USA 300的saeR/S等基因缺失突变体（USA 300？saeR/S）显示与USA 300相比感染的发生率和严重程度显著降低。在体外寡核苷酸芯片和实时逆转录聚合酶链反应测定确定了许多细胞外毒力基因下调USA 300？saeR/S和重组SaeR与毒力基因启动子内共有序列的直接结合。在主机方面，我们已经确定，SaeR/S的影响因素改变当地生产的促炎细胞因子IFN？TNF？在软组织感染的过程中。基于初步的数据，我们假设毒力因子在SaeR/S的直接影响下调节S的严重性。金黄色皮肤感染。我们将以两个具体目标来检验这一假设。在具体目标1中，我们将确定SaeR是否直接调节S。金黄色葡萄球菌在皮肤感染过程中体内毒力基因。通过建立同基因突变体并研究其对葡萄球菌致病机制的影响，将探讨saeR/S调控的毒力因子的特定作用。在具体目标2中，我们将通过检验SaeR/S调节因子降低TNF？增加IFN？在葡萄球菌皮肤感染期间促进发病。总的来说，这项研究将通过鉴定特定的S。金黄色葡萄球菌因子，促进皮肤感染，并可能有潜在的影响，使用免疫调节疗法治疗链球菌。金黄色葡萄球菌感染鉴于我们目前抗生素的有效性不断下降，很明显，我们必须提高对S的分子机制的理解。金黄色葡萄球菌的毒力，以控制由这种可能危及生命的病原体引起的疾病。 公共卫生相关性：金黄色葡萄球菌（S。金黄色葡萄球菌）是世界范围内发病率和死亡率的主要原因。社区内高感染性社区相关耐甲氧西林（CA-MRSA）菌株的出现是一个主要的公共卫生问题。鉴于目前抗生素的有效性正在减弱，很明显我们必须提高对S的基本分子机制的理解。金黄色葡萄球菌的致病机理，以便开发更好的方法来控制/治疗CA-MRSA疾病，从而改善公众健康。

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.