Mechanisms of Glycopeptide Resistance in Staphylococci

描述（由申请人提供）：金黄色葡萄球菌是社区和医院获得性感染和毒素介导综合征的主要原因，有些危及生命，影响所有年龄段的患者。糖肽类药物是目前治疗链球菌病最可靠的药物。金黄色葡萄球菌分离株对甲氧西林耐药，对所有β-内酰胺类交叉耐药，并且通常对广谱不相关的抗菌剂耐药。然而，GP的有效性已被越来越多的耐药菌株的认识所侵蚀。我们正在进行的研究旨在确定GP耐药机制。尽管抗性菌株的表型和生化特性有很多描述，但S.金黄色葡萄球菌仍然没有完全定义。现有数据表明，获得的耐药表型涉及细胞壁重组;多效性变化已被记录，如改变肽聚糖结构，凝固酶活性，结合万古霉素，自溶活性和溶葡萄球菌酶敏感性。然而，它似乎不太可能是一个单一的机制或机制序列将占所有临床糖肽耐药菌株研究至今，因为没有表型或生化变化已被均匀发现。我们认为，耐药表型涉及多种遗传变化。我们计划采用多管齐下的方法研究耐药机制。首先，利用四个S.我们将利用微阵列分析比较GP敏感株和耐药株之间相关细胞壁代谢和双组分信号转导基因的表达模式。同基因敏感和耐药临床分离株对的可用性将为这种分析提供宝贵的工具。适当的上调和下调基因将被作为进一步研究的目标，包括序列比较、北方印迹分析、等位基因失活和相关遗传背景中的过表达。这些研究有助于理解S.金黄色葡萄球菌抵抗GP的杀菌作用，并有望确定关于由耐药菌株引起的感染的治疗的新思路。

DESCRIPTION (provided by applicant): Staphylococcus aureus is a leading cause of community and nosocomially-acquired infectious and toxin-mediated syndromes, some life threatening, that affect patients of all ages. The glycopeptides (GP) have been the most reliable alternatives for the therapy of S. aureus isolates that are resistant to methicillin, cross resistant to all beta-lactams, and often resistant to a wide spectrum of unrelated antimicrobials. However, the effectiveness of GPs has been eroded by the increasing recognition of resistant isolates. Our ongoing studies are aimed at identifying GP resistance mechanisms. Despite the description of numerous phenotypic and biochemical characteristics among resistant isolates, the mechanism(s) of GP resistance in S. aureus has remained incompletely defined. Available data suggest that acquisition of the resistance phenotype involves cell wall reorganization; pleiotropic changes have been documented such as altered peptidoglycan structure, coagulase activity, binding of vancomycin, autolytic activity and lysostaphin susceptibility. However, it seems unlikely that a single mechanism or sequence of mechanisms will account for resistance in all clinical glycopeptide-resistant isolates studied to date since no phenotypic or biochemical change has been uniformly found. We believe that the resistant phenotype involves multiple genetic changes. We plan to investigate the mechanism(s) of resistance with a multi-pronged approach. First, with the complete genomic sequence of four S. aureus isolates at hand, we will employ microarray analysis to compare expression patterns of relevant cell wall metabolic and 2-component signal transduction genes between GP-susceptible and resistant isolates. The availability of isogenic susceptible and resistant clinical isolate pairs will provide invaluable tools for this analysis. Appropriate up and down regulated genes will be targeted for further investigation including sequence comparison, Northern blot analysis, allelic inactivation and overexpression in relevant genetic backgrounds. These studies should lead to an understanding of the mechanisms by which S. aureus resist the bactericidal effect of GPs and hopefully can identify new ideas regarding therapy of infections caused by resistant isolates.