The Role of SaeR/S During Staphylococcus aureus Skin Infections

描述(申请人提供)：金黄色葡萄球菌(金黄色葡萄球菌)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。最近的一份报告指出，耐甲氧西林金黄色葡萄球菌(MRSA)是美国各地急诊科感染的主要原因，约占皮肤和软组织感染的59%。社区相关的MRSA菌株USA300被确定为这些感染中97%的病原体。这项建议的目的是探索金黄色葡萄球菌在宿主-病原体界面上使用的特定分子机制。由于社区相关耐甲氧西林金黄色葡萄球菌USA300株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株中的作用。USA300的Saer/S等基因缺失突变株(USA300？Saer/S)的感染发生率和严重程度明显低于USA300。体外寡核苷酸芯片和实时定量逆转录聚合酶链式反应检测到大量的胞外毒力基因在USA300、SAER/S中表达下调，重组SAER直接与毒力基因启动子内的一个共同序列结合。在宿主方面，我们已经确定了Saer/S影响因素改变了局部促炎细胞因子干扰素？那肿瘤坏死因子呢？在软组织感染期间。根据初步数据，我们假设在SAER/S直接影响下的毒力因子调节金黄色葡萄球菌皮肤感染的严重程度。我们将通过两个具体目标来检验这一假设。在特定的目标1中，我们将确定在皮肤感染过程中，SAER是否直接调节体内金黄色葡萄球菌的毒力基因。通过创建等基因突变株并研究它们对葡萄球菌致病机制的影响，将寻求SAER/S调节的毒力因子的特定作用。在特定目标2中，我们将通过检验SAER/S调节的因子降低肿瘤坏死因子？的假设来定义SAER/S特异性的宿主反应。并增加干扰素？促进葡萄球菌皮肤感染的发病机制。总而言之，这项研究将通过识别促进皮肤感染的特定金黄色葡萄球菌因子来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具有潜在的意义。鉴于我们目前抗生素的有效性正在减弱，显然我们必须更好地了解金黄色葡萄球菌毒力的基本分子机制，以控制这种潜在威胁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.aureus)是全球发病率和死亡率的主要原因。社区内出现高传染性社区相关甲氧西林耐药(CA-MRSA)菌株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，显然我们必须提高对金黄色葡萄球菌致病的基本分子机制的理解，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.