Regulation/mecA gene expression/clinic S.aureus isolates

描述(申请人提供)：全球医院获得性感染治疗面临的最严重挑战之一是对所有β-内酰胺类抗生素耐药的葡萄球菌的出现和全球传播(称为耐甲氧西林金黄色葡萄球菌；MRSA)。葡萄球菌可通过获得编码β-内酰胺不敏感靶标酶青霉素结合蛋白(PBP)2a的基因(MecA)而对β-内酰胺类抗生素产生抗药性。这种酶使细菌能够交联细胞壁并生长，而细胞中常见的交联酶(PBP)被β-内酰胺类抗生素结合并失活。大多数金黄色葡萄球菌还产生Blaz编码的/β-内酰胺酶，该酶能水解β-内酰胺类抗生素，使其失去活性。MecA和BlaZ的转录分别由相关的差异转录的两个基因操纵子mecRl-mecI和blaRl-BLAI调控，这两个操纵子分别编码一个信号转导子(R1)和一个抑制子(I)。这项建议中概述的正在进行的研究是基于先前在实验室菌株中的观察结果，这些观察结果证明了MecI和BLAI对mecA的共同调节。此外，这些观察结果可以扩展到为了生存/β-内酰胺压力而逃脱MecI抑制的临床相关菌株(36)。这项建议的目的是提供证据，证明存在参与或需要甲氧西林耐药诱导表达的其他基因座。这些数据将为研究MecR1/BlaR1和MecI/BLAI信号转导的分子基础提供有价值的结构/功能信息。其具体目的是：通过鉴定和鉴定可能促进mecA/blAZ表达的“mecR2”基因，研究MecR1/BlaR1向MecI/Blal信号转导的分子基础。为了验证这样一种假设，即抑制基因在进化上是保守的，以防止有毒的、受调控的基因产物过度生产。具体地说，我们将评估在没有β-内酰胺诱导的情况下，MecR1/BlaR1或其相应的突变体/缺失体的可诱导过表达是否会对细胞产生毒性影响。

DESCRIPTION (provided by applicant): One of the most serious contemporary challenges to the treatment of hospital-acquired infections worldwide is the appearance and global spread of staphylococci resistant to all beta-lactam antibiotics (known as methicillin-resistant S. aureus; MRSA). Staphylococci can become resistant to Beta-lactam antibiotics by acquiring a gene (mecA) that encodes a beta-lactam insensitive target enzyme, penicillin binding protein (PBP)2a. This enzyme affords the bacterium the ability to cross-link cell wall and grow while the cell's usual cross-linking enzymes (PBP's) are bound and inactivated by Beta-lactam antibiotics. Most of S. aureus also produce/beta-lactamase encoded by blaZ, which can hydrolyse Beta-lactam antibiotics rendering them inactive. The transcription of mecA and blaZ is regulated by related divergently transcribed two-gene operons mecRl-mecI and blaRl-blaI, respectively that encode a signal transducer (R1) and a repressor (I). The ongoing studies outlined in this proposal are based on previous observations in laboratory strains that demonstrated the coregulation of mecA by both MecI and BlaI Furthermore, these observations could be extended to clinically relevant isolates which escape MecI repression in order to survive/beta-lactam pressure (36). The goal of this proposal is to provide evidence of the existence of additional loci involved in or required for inducible expression of methicillin resistance. These data will provide valuable structure/function information to complement studies investigating the molecular basis of MecR1/BlaR1 and MecI/BlaI signal transduction. The specific aims are: To Investigate the molecular basis of signal transduction through MecR1/BlaR1 to MecI/Blalby identifying and characterizing "mecR2" loci - chromosomal genes that may contribute to the induction of mecA/blaZ expression. To test the hypothesis that repression is evolutionarily conserved in order to prevent overproduction of a toxic, regulated gene product. Specifically, we will evaluate if the inducible overexpression of either MecR1/BlaR1 or their corresponding mutants/deletants in the absence of Beta-lactam induction results in a toxic effect to the cell.