Staphylococcal methicillin resistance locus

描述（由申请人提供）：葡萄球菌是医院获得性感染的主要原因，尤其是医院内菌血症。两种最有效和最广泛使用的抗葡萄球菌治疗剂是糖肽和β-内酰胺，两者都靶向细胞壁生物合成。然而，随着耐药性的发展，这些药物的治疗效果越来越差，首先是对β-内酰胺类，最近是对糖肽类。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标，即一种不会被抗生素灭活的细胞壁转肽酶或青霉素结合蛋白（PBP 2a）。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在一个名为SCCmec的致病岛内编码。以下建议旨在继续研究，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剂产生抗性所需的基因组适应。第一个具体目标是研究SCCmec在金黄色葡萄球菌（SA）菌株之间的转移，以及来自不同葡萄球菌菌种S。表皮（SE）至SA。有证据表明，一个新的SCCmec类型，IV型，最近已进入SA分离流行的社区，它是目前在大多数SE分离。将研究该元件的切除、转移（通过质粒和噬菌体）和重新插入。 第二个具体目标将是继续研究通过传感器/换能器MecR 1诱导mecA转录，导致转录阻遏物Mecl从其DNA结合位点释放。将通过构建嵌合分子、确定阻遏物的晶体结构和鉴定诱导所需的其他染色体基因来评估诱导物和阻遏物的信号转导基础和蛋白水解裂解作用。第三个具体目标将是证实和扩展通过微阵列转录谱分析所做的观察，即嘌呤生物合成在对万古霉素和苯唑西林产生高水平耐药性的菌株中发生改变，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遗传操纵并与VR和OR的发展相关。此外，微阵列和蛋白质组学研究将追求对其他代理人扰乱细胞壁。

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.