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，一些危及生命，影响所有年龄段的患者。糖肽（GP）一直是治疗对甲氧西林耐药、对所有β -内酰胺交叉耐药以及对广泛的不相关抗菌素耐药的金黄色葡萄球菌分离株的最可靠的替代方案。然而，由于越来越多的人认识到耐药菌株，全科医生的有效性受到了削弱。我们正在进行的研究旨在确定GP耐药机制。尽管在耐药菌株中描述了许多表型和生化特征，但金黄色葡萄球菌对GP耐药的机制仍然不完全确定。现有数据表明，抗性表型的获得涉及细胞壁重组；多效性变化已被证实，如肽聚糖结构、凝固酶活性、万古霉素结合、自溶活性和溶葡萄球菌素敏感性的改变。然而，单一机制或一系列机制似乎不太可能解释迄今为止研究的所有临床糖肽耐药分离株的耐药，因为没有统一发现表型或生化变化。我们认为抗性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，有了4株金黄色葡萄球菌的完整基因组序列，我们将采用微阵列分析来比较gp敏感和耐药菌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。等基因易感和耐药临床分离对的可用性将为这一分析提供宝贵的工具。合适的上调和下调基因将在相关遗传背景下进行序列比较、Northern blot分析、等位基因失活和过表达等进一步研究。这些研究将有助于了解金黄色葡萄球菌抵抗全科医生杀灭细菌作用的机制，并有望为耐药菌株引起的感染治疗提供新的思路。

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.