Genetic Basis of Virulence of Community MRSA Clone USA300

社区 MRSA 克隆 ​​USA300 毒力的遗传基础

• 批准号: 7461989
• 负责人: Henry F HENRY CHAMBERS
• 金额: $ 38.27万
• 依托单位: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-04-01 至 2011-03-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7461989
• 关键词: Acquired Immunodeficiency Syndrome; Adherence; Adhesions; Affect; Animal Model; Antibiotic Resistance; Antibiotics; Antibodies; Arginine; Attenuated; Bacteremia; Bacteria; Be++ element; Beryllium; Biological Assay; Cells; Chemotaxis; Code; Communities; Complement Inactivators; Condition; Cytolysis; Development; Disease; Disruption; Drug resistance; Elements; Enterotoxins; Epidemic; Eukaryotic Cell; Exposure to; Gene Cluster; Genes; Genetic; Genomic Islands; Genomics; Genus staphylococcus; Host Defense; Human; Immune; In Vitro; Indium; Infection; Invasive; Learning; Lung; Measures; Mobile Genetic Elements; Modeling; Monobactams; Mutation; Negative Finding; Organ; Organ Specificity; Oryctolagus cuniculus; Panton-Valentine leukocidin; Parents; Pathogenesis; Pathogenicity Island; Penicillins; Phagocytosis; Pharmaceutical Preparations; Platelet Factor 4; Pneumonia; Prevention approach; Production; Prophages; Protein S; Proteins; Public Health; Research; Resistance; Role; SOS Response; Staphylococcal Infections; Staphylococcus aureus; Staphylococcus aureus auR protein; Superantigens; Testing; Tissues; Toxin; United States; Virulence; Virulence Factors; Virulent; base; beta-Lactam Resistance; in vitro Assay; killings; methicillin resistant Staphylococcus aureus; mutant; neutrophil; novel; novel therapeutics; pathogen; research study

DESCRIPTION (provided by applicant): Staphylococcus aureus is a major human pathogen. It can cause rapidly fatal infections. A highly virulent clone of methicillin resistant S. aureus (MRSA), USA300, is epidemic in communities in the United States. MRSA is resistant to all antibiotics chemically related to penicillin, thus emergence of this clone is a serious public health issue. Our research objective is to identify genes that contribute to virulence of USA300. Emergence of USA300 is associated with acquisition of certain mobile genetic elements, which we suspect carry genes that impact virulence. To test this hypothesis, mutants of USA300 in which suspected virulence genes have been deleted will be tested in rabbit infection models and in vitro assays to determine if their virulence is reduced compared to the normal strain. Polymorphonuclear neutrophils (PMNs) are the first line of innate host defense against S. aureus infection and are critical for bacterial clearance. PMN function will be assayed in vitro to determine whether virulence factors affect human PMN chemotaxis, phagocytosis, or bacterial killing. Specific aims are: 1) To identify virulence determinants in the arginine catabolic mobile element (ACME), which is unique to USA300. Deletion of ACME reduces virulence. Three "likely suspect virulence genes, arcA, opp-3A and opp-3DF, will be deleted and each mutant tested to determine which impact virulence. 2) To determine whether SOS response induced by non-lethal exposure to beta-lactam antibiotic generates adaptive mutations offering a survival advantage to MRSA. 3) To determine if disruption of PVL genes attenuates virulence in a rabbit pneumonia model. PVL (Panton-Valentine leukocidin) is generally assumed to be the most important virulence factor in USA300, but this is highly controversial. The rabbit as a species is sensitive to PVL and lung may be target organ. Results from this model should help resolve the controversy as to whether PVL is a major virulence factor. 4) To determine whether genes within two other elements, (Sa3 prophage and SaPI5 pathogenicity island, encode virulence determinants. Relevance: Emergence of virulent, drug-resistant strains of S. aureus in the community is a public problem second only to AIDS in scope and importance. Defining genes contributing to the special virulence of USA300 strains is a critical first step for developing new drugs and approaches for treatment of severe infections caused by community-associated MRSA strains. PUBLIC HEALTH RELEVANCE Antibiotic resistant strains of Staphylococcus aureus, an important human pathogen, are on the rise. One particular clone, USA300, seems to be especially virulent. Several genes that could be important for virulence are uniquely present in USA300. By knocking each of these genes out and testing for loss of virulence, we hope to learn which genes code for virulence. Once these genes are identified, strategies to block their effects may be developed.

描述（申请人提供）：金黄色葡萄球菌是一种主要的人类病原体。它可以引起迅速致命的感染。耐甲氧西林金黄色葡萄球菌（MRSA）的高毒力克隆USA300在美国社区流行。MRSA对所有与青霉素化学相关的抗生素都具有耐药性，因此这种克隆体的出现是一个严重的公共卫生问题。我们的研究目标是鉴定与USA300毒力有关的基因。USA300的出现与某些移动遗传元件的获得有关，我们怀疑这些元件携带影响毒力的基因。为了验证这一假设，将在家兔感染模型和体外试验中测试USA300疑似毒力基因被删除的突变体，以确定它们的毒力是否比正常菌株降低。多形核中性粒细胞（pmn）是先天宿主防御金黄色葡萄球菌感染的第一道防线，对细菌清除至关重要。将在体外检测PMN的功能，以确定毒力因素是否影响人PMN趋化性、吞噬作用或细菌杀灭。具体目的是：1)确定USA300特有的精氨酸分解代谢移动元件（ACME）的毒力决定因素。删除ACME可降低毒力。三个“可能怀疑的毒力基因，arcA， opp-3A和opp-3DF，将被删除，并对每个突变进行测试，以确定哪种影响毒力。”2)确定非致死暴露于β -内酰胺抗生素诱导的SOS反应是否会产生适应性突变，从而为MRSA提供生存优势。3)确定PVL基因的破坏是否会降低兔肺炎模型的毒力。PVL （Panton-Valentine leukocidin）通常被认为是USA300中最重要的毒力因子，但这一观点存在很大争议。兔作为对PVL敏感的物种，肺可能是其靶器官。该模型的结果将有助于解决PVL是否是主要毒力因子的争议。4)确定Sa3原噬菌体和SaPI5致病性岛内的基因是否编码毒力决定因子。相关性：在社区中出现的毒力强、耐药的金黄色葡萄球菌菌株是一个范围和重要性仅次于艾滋病的公共问题。确定导致USA300菌株特殊毒力的基因是开发治疗由社区相关MRSA菌株引起的严重感染的新药和方法的关键的第一步。金黄色葡萄球菌是一种重要的人类病原体，耐抗生素菌株呈上升趋势。一个特殊的克隆，USA300，似乎是特别致命的。几个可能对毒力很重要的基因在USA300中是唯一存在的。通过敲除这些基因中的每一个，并测试毒性的丧失，我们希望了解哪些基因编码毒性。一旦确定了这些基因，就可以开发出阻止其影响的策略。