Staphylococcal methicillin resistance locus

描述(申请人提供)：葡萄球菌是医院获得性感染的主要原因，特别是医院内菌血症。两种最有效和使用最广泛的抗葡萄球菌治疗药物是糖肽和β-内酰胺类药物，这两种药物都是针对细胞壁的生物合成。然而，随着耐药性的产生，这些药物的治疗正在变得不那么有效，首先是对β-内酰胺类药物，最近是对糖肽类药物的耐药性。对β-内酰胺类抗生素耐药的最重要机制是获得一个新的靶点，一种不被抗生素灭活的细胞壁转肽酶或青霉素结合蛋白(PBP2a)。这种类型被称为甲氧西林或苯唑西林耐药性(OR)，介导这种耐药性的基因mecA编码在一个称为SCCmec的致病岛上。以下提议寻求继续进行研究，探索介导OR的基因的起源、传播和调控，以及葡萄球菌对破坏其细胞壁的药物产生抗药性所需的基因组适应。第一个具体目标将是研究SCCmec在金黄色葡萄球菌(SA)菌株之间以及从另一种葡萄球菌表皮葡萄球菌(SE)向SA的转移。有证据表明，一种新的SCCmec类型，类型IV，最近进入了社区中流行的SA分离物，它存在于大多数SE分离物中。将对该元件的切除、转移(通过质粒和噬菌体)和重新插入进行研究。 第二个具体目标将是继续研究通过传感器/转导分子MecR1诱导mecA转录，导致转录抑制因子Mec1从其DNA结合部位释放。通过构建嵌合分子、确定阻遏子的晶体结构和鉴定诱导所需的额外染色体基因，将评估信号转导的基础和诱导子和阻遏子的蛋白水解性切割的作用。第三个具体目标将是证实和扩大微阵列转录图谱的观察结果，即对万古霉素和苯唑西林产生高水平耐药性的菌株的嘌呤生物合成发生改变，但方向相反(分别增加和减少)。这两种表型似乎是相互排斥的。嘌呤生物合成操纵子将被基因操纵，并与VR和OR的发展相关。此外，还将对扰乱细胞壁的其他制剂进行微阵列和蛋白质组学研究。

DESCRIPTION (provided by applicant): Staphylococci are the leading cause of hospital-acquired infections, especially nosocomial bacteremia. The two most effective and widely used anti-staphylococcal therapeutic agents are glycopeptides and beta-lactams, both of which target cell wall biosynthesis. However, therapy with these agents is becoming less effective as resistance has developed, first to beta-lactams and, more recently, to glycopeptides. The most important mechanism of resistance to beta-lactams is the acquisition of a new target, a cell wall transpeptidase or penicillin binding protein (PBP2a) that is not inactivated by the antibiotic. This type is called methicillin or oxacillin resistance (OR) and the gene that mediates this resistance, mecA, is encoded within a pathogenicity island called SCCmec. The following proposal seeks to continue studies that explore the origin, dissemination and regulation of genes that mediate OR and genomic adaptations required for staphylococci to become resistant to agents that damage their cell walls. The First Specific Aim will be to investigate the transfer of SCCmec between strains of Staphylococcus aureus (SA) and from a different staphylococcal species, S. epidermidis (SE), to SA. There is evidence that a new SCCmec type, Type IV, has recently moved into SA isolates prevalent in the community and it is present in the majority of SE isolates. The excision, transfer (by plasmid and phage) and reinsertion of this element will be investigated. The Second Specific Aim will be to continue studies on the induction of mecA transcription through the sensor/transducer, MecR1, resulting in the release of the transcriptional repressor, Mecl, from its DNA binding site. The basis of signal transduction and role of proteolytic cleavage of inducer and repressor will be assessed by constructing chimeric molecules, determining the crystal structure of repressors and identifying additional chromosomal genes required for induction. The Third Specific Aim will be to confirm and expand observations made by microarray transcriptional profiling that purine biosynthesis is altered in strains that develop high level resistance to vancomycin and oxacillin, but in opposite directions (increased and decreased respectively). These two phenotypes appear to be mutually exclusive. The purine biosynthetic operons will be genetically manipulated and correlated with development of VR and OR. In addition, microarray and proteomic studies will be pursued on other agents that perturb the cell wall.