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: 7591811
• 负责人: Henry F HENRY CHAMBERS
• 金额: $ 38.63万
• 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/7591811
• 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; Cytolysis; Development; Disease; 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; 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 therapeutic intervention; pathogen; public health relevance; research study; resistant strain

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（由申请人提供）：金黄色葡萄球菌是主要的人类病原体。它会导致迅速致命的感染。耐甲氧西林金黄色葡萄球菌 (MRSA) 的高毒力克隆 USA300 在美国社区中流行。 MRSA 对所有与青霉素化学相关的抗生素具有耐药性，因此该克隆的出现是一个严重的公共卫生问题。我们的研究目标是确定导致 USA300 毒力的基因。 USA300 的出现与某些可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。为了检验这一假设，我们将在兔子感染模型和体外测定中对疑似毒力基因已被删除的 USA300 突变体进行测试，以确定其毒力与正常菌株相比是否有所降低。多形核中性粒细胞 (PMN) 是宿主抵抗金黄色葡萄球菌感染的第一道防线，对于细菌清除至关重要。将在体外检测中性粒细胞功能，以确定毒力因子是否影响人类中性粒细胞趋化性、吞噬作用或细菌杀灭作用。具体目标是： 1) 确定 USA300 所独有的精氨酸分解代谢移动元件 (ACME) 中的毒力决定因素。删除 ACME 会降低毒力。将删除三个“可能可疑的毒力基因，arcA、opp-3A 和 opp-3DF，并对每个突变体进行测试以确定哪个突变体影响毒力。2) 确定非致死性接触 β-内酰胺抗生素诱导的 SOS 反应是否产生适应性3) 确定 PVL 基因的破坏是否会减弱兔肺炎模型中的毒力。是 USA300 中最重要的毒力因子，但兔子作为一个物种对 PVL 敏感，并且肺可能是靶器官，该模型的结果应该有助于解决关于 PVL 是否是主要毒力因子的争议。 4) 确定其他两个元件（Sa3 原噬菌体和 SaPI5 致病性岛）中的基因是否编码毒力决定子。相关性：金黄色葡萄球菌的毒力、耐药菌株的出现是一个在范围和重要性上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新方法的关键第一步。公共卫生相关性 金黄色葡萄球菌（一种重要的人类病原体）的抗生素耐药菌株正在增加。一种特殊的克隆，USA300，似乎具有特别强的毒性。 USA300 中独特存在几个可能对毒力很重要的基因。通过敲除这些基因并测试毒力的丧失，我们希望了解哪些基因编码毒力。一旦识别出这些基因，就可以制定阻止其影响的策略。