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; 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）：我们的长期目标是对细菌适应性和毒力如何相交的发病机理的更深入了解。本提案的重点是葡萄球菌virulon在社区获得的耐甲氧西林金黄色葡萄球菌（CA-MRSA）引起的感染中的作用。尽管CA-MRSA遭遇的结果通常是无症状的定植，但CA-MRSA菌株产生侵入性感染的倾向定义了抵抗宿主先天免疫清除机制的能力。负责这种重要宿主 - 病原体相互作用的各种结果的CA-MRSA因子尚不清楚。 AGR基因座是毒力基因表达的全球调节剂，由于其在动物模型中的侵袭性中的关键作用，因此受到了很多关注。我们的初步数据表明，人类中CA-MRSA的侵袭伴随着具有增强AGR活性变体的富集支持这一想法，并表明疾病的早期阶段伴随细菌变化，引起了侵入性的疾病疾病。这种变体的DNA测序表明，AGR基因座没有改变，表明“上游” AGR调节有助于表型。替代Sigma因子SigB的功能障碍被确定为表型的常见原因，但是我们对临床分离株的初步调查表明，其他未知基因的变化发生。至关重要的是，变体在体外具有健身优势，这表明独立于宿主因素的选择压力可以部分解释其出现。这些考虑因素引起了以下两部分假设，目前的提议基于：1）通过基因突变，金黄色葡萄球菌经常在感染中产生一组克隆在其毒力上不同的克隆，而2）CA-MRSA菌株的转移从共同体转移到具有诱人的疾病现象相关的vivo中，以增强了变异的变化。为了检验假设，我们将1）确定临床CA-MRSA皮肤感染和侵入性疾病期间AGR功能内宿内上升的频率，2）2）表征这些升级的遗传基础，3）评估菌株的相对毒力和适应性，均具有上流体外的体外菌株 并使用串行通过和竞争测试进行体内。现场研究将集中于社区受试者，在社区受试者中，感染的障碍高于住院的患者，这些患者因疾病和临床干预而破坏障碍功能，允许金黄色葡萄球菌菌株缺乏全部毒力引起感染。拟议的工作将影响传染病研究中的关键问题，例如最佳利用正在开发的治疗方法，这些方法是针对AGR和毒力的，以及更基本但密切相互交织的问题，例如金黄色葡萄球菌从我们正常植物群的无辜成员转变为一种无辜的人，向无辜的，无与伦比的，生命的，生命的，现实的，构成了生命的病情。这项工作将对阻止此类事件具有广泛的影响。