Role of precipitous virulence in invasiveness of community-acquired methicillin-r

急剧毒力在社区获得性甲氧西林-r侵袭性中的作用

• 批准号: 8774580
• 负责人: BO SHOPSIN
• 金额: $ 42.38万
• 依托单位: NEW YORK UNIVERSITY SCHOOL OF MEDICINE
• 依托单位国家: 美国
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-12-01 至 2015-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8774580
• 关键词: Abscess; Accounting; Acute; Affect; Alien; Animal Model; Anti-Infective Agents; Attention; Bacteria; Biological Assay; Cell Density; Chromosome Mapping; Clinical; Communities; Cutaneous; DNA Sequence; Data; Defect; Disease; Event; Exhibits; Frequencies; Functional disorder; Gene Expression; Gene Expression Regulation; Gene Mutation; Genes; Genetic; Genetic Variation; Goals; Health; Host Defense; Human; In Vitro; Individual; Infection; Infectious Diseases Research; Infectious Skin Diseases; Integration Host Factors; Intervention; Knowledge; Lead; Life; Life Style; Methicillin; Microbial Biofilms; Minority; Modality; Mutation; Outcome; Pathogenesis; Patients; Phenotype; Play; Population; Production; Property; Recovery; Regulation; Regulator Genes; Relative (related person); Research; Rest; Role; Serial Passage; Sigma Factor; Site; Staging; Staphylococcus aureus; Surveys; Testing; Therapeutic; Therapeutic Uses; Time; Tissues; Toxin; Variant; Virulence; Virulent; Work; base; comparative; design; disease phenotype; field study; fitness; genome sequencing; immune clearance; in vivo; knockout gene; member; methicillin resistant Staphylococcus aureus; mutant; pathogen; pressure; prevent; programs; quorum sensing; screening

DESCRIPTION (provided by applicant): Our long-term goal is a deeper understanding of how bacterial fitness and virulence intersect in pathogenesis. The present proposal focuses on the role of the Staphylococcal virulon in infections caused by community- acquired, methicillin-resistant Staphylococcus aureus (CA-MRSA). While the outcome of a CA-MRSA encounter is usually asymptomatic colonization, the propensity of CA-MRSA strains to produce invasive infection defines a capacity to resist host innate immune clearance mechanisms. The CA-MRSA factors responsible for the diverse outcomes of this important host-pathogen interaction are unknown. The agr locus, a global regulator of virulence gene expression, has received much attention due to its critical role in invasiveness in animal models. Our preliminary data suggesting that invasion of CA-MRSA in humans is accompanied by enrichment for variants with enhanced agr activity supports this idea and indicates that the early stages of disease are accompanied by bacterial changes that give rise to an invasive-disease phenotype. DNA sequencing of such variants revealed that the agr locus was unaltered, indicating that "upstream" agr regulation contributes to the phenotype. Dysfunction of the alternative sigma factor sigB was identified as a frequent cause of the phenotype, but our preliminary survey of clinical isolates indicates the occurrence of alterations in other, unknown genes. Critically, variants had a fitness advantage in vitro, suggesting that selective pressures independent of host factors can account in part for their emergence. These considerations give rise to the following two-part hypothesis, upon which the present proposal is based: 1) through mutation of genes, S. aureus frequently generates within an infection a group of clones differing in their virulence, and 2) the shift of CA-MRSA strains from a commensal to an invasive-disease phenotype is associated with selection in vivo for mutations that enhance virulence. To test the hypothesis, we will 1) determine the frequency of within-host upshifts in agr function during clinical CA-MRSA skin infection and invasive disease, 2) characterize the genetic basis of these upshifts, and 3) evaluate the relative virulence and fitness of strains with upshifts both in vitro and in vivo using serial passage and competition tests. Field studies will focus on community subjects, where the barrier to infection is higher than in hospitalized patients for whom disruption of barrier functions by disease and clinical intervention permit S. aureus strains that lack full virulence to cause infection. The proposed work will impact critical questions in infectious disease research, such as the best use of therapeutic modalities that are being developed to target agr and virulence, as well as more basic yet closely intertwined problems, such as the ways in which S. aureus transitions from an innocent member of our normal flora to an invasive, life-threatening pathogen. The work will have broad implications for forestalling such events.

描述（由申请人提供）：我们的长期目标是更深入地了解细菌适应性和毒力在发病机制中如何交叉。本提案重点关注葡萄球菌病毒在社区获得性耐甲氧西林金黄色葡萄球菌 (CA-MRSA) 引起的感染中的作用。虽然 CA-MRSA 遭遇的结果通常是无症状定植，但 CA-MRSA 菌株产生侵袭性感染的倾向决定了其抵抗宿主先天免疫清除机制的能力。造成这一重要宿主-病原体相互作用的不同结果的 CA-MRSA 因素尚不清楚。 agr位点是毒力基因表达的全局调节因子，由于其在动物模型侵袭性中的关键作用而受到广泛关注。我们的初步数据表明，CA-MRSA 对人类的入侵伴随着 agr 活性增强的变异体的富集，这支持了这一观点，并表明疾病的早期阶段伴随着细菌的变化，从而产生了侵袭性疾病表型。这些变体的 DNA 测序显示 agr 基因座没有改变，表明“上游”agr 调控对表型有贡献。替代西格玛因子 sigB 的功能障碍被认为是该表型的常见原因，但我们对临床分离株的初步调查表明其他未知基因发生了改变。至关重要的是，变异体在体外具有适应性优势，这表明独立于宿主因素的选择压力可以部分解释它们的出现。这些考虑引出了以下由两部分组成的假设，本建议基于该假设：1）通过基因突变，金黄色葡萄球菌经常在感染内产生一组毒力不同的克隆，2）CA-MRSA菌株从共生表型向侵袭性疾病表型的转变与体内选择增强毒力的突变有关。为了检验这一假设，我们将 1) 确定临床 CA-MRSA 皮肤感染和侵袭性疾病期间 agr 功能在宿主内上调的频率，2) 描述这些上调的遗传基础，以及 3) 评估体外上调菌株的相对毒力和适应性 并在体内使用连续传代和竞争测试。实地研究将集中于社区受试者，这些受试者的感染屏障高于住院患者，因为疾病和临床干预对屏障功能的破坏使得缺乏完全毒力的金黄色葡萄球菌菌株能够引起感染。拟议的工作将影响传染病研究中的关键问题，例如针对农业和毒力正在开发的治疗方式的最佳利用，以及更基本但紧密交织的问题，例如金黄色葡萄球菌如何从我们正常菌群的无辜成员转变为侵入性的、危及生命的病原体。这项工作将对预防此类事件产生广泛的影响。