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: 8970671
• 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 2017-11-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/8970671
• 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; Research; Rest; Role; Serial Passage; Sigma Factor; Site; Staging; Staphylococcus aureus; Surveys; Testing; Therapeutic; Therapeutic Uses; Time; Tissues; Toxin; Variant; Virulence; Virulent; Work; bacterial fitness; base; comparative; design; disease phenotype; field study; fitness; fitness test; genome sequencing; immune clearance; in vivo; individual patient; knockout gene; member; methicillin resistant Staphylococcus aureus; mutant; pathogen; pressure; prevent; programs; quorum sensing; screening; whole genome

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如何在发病机制中交叉。目前的建议集中在葡萄球菌的作用，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。虽然CA-MRSA遭遇的结果通常是无症状的定殖，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。CA-MRSA的因素负责这种重要的宿主-病原体相互作用的不同结果是未知的。agr基因座是一个全局性的毒力基因表达调控基因，由于其在动物模型中的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在人类中的入侵伴随着具有增强agr活性的变异体的富集，这支持了这一观点，并表明疾病的早期阶段伴随着细菌变化，这些细菌变化引起侵袭性疾病表型。这些变体的DNA测序显示，agr基因座是不变的，表明“上游”agr调节有助于表型。替代因子sigB的功能障碍被确定为表型的常见原因，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。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。这些考虑引起了以下两部分假设，本建议是基于：1）通过基因突变，S。金黄色葡萄球菌在感染中经常产生一组毒力不同的克隆，2）CA-MRSA菌株从寄生性疾病表型到侵袭性疾病表型的转变与体内选择增强毒力的突变有关。为了验证这一假设，我们将1）确定临床CA-MRSA皮肤感染和侵袭性疾病期间宿主内agr功能上调的频率，2）表征这些上调的遗传基础，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试验。现场研究将集中在社区受试者，那里的感染屏障高于住院患者，对他们来说，疾病和临床干预允许屏障功能的破坏。缺乏引起感染的完全毒力的金黄色葡萄球菌菌株。拟议的工作将影响传染病研究中的关键问题，例如正在开发的针对agr和毒力的治疗方式的最佳使用，以及更基本但紧密交织的问题，例如S.金黄色葡萄球菌从我们正常植物群的无辜成员转变为侵入性的、威胁生命的病原体。这项工作将对预防此类事件产生广泛影响。