Mechanisms of Glycopeptide Resistance in Staphylococci

描述(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性综合征的主要原因，一些危及生命，影响所有年龄的患者。糖肽(GP)已成为治疗耐甲氧西林金黄色葡萄球菌、对所有β-内酰胺类抗生素交叉耐药以及对多种无关抗菌药耐药的最可靠的替代药物。然而，由于对耐药菌株的认识不断增加，GPs的有效性已经受到侵蚀。我们正在进行的研究旨在确定GP耐药机制。尽管金黄色葡萄球菌耐药株的表型和生化特征已有报道，但金黄色葡萄球菌耐药机制(S)仍不完全清楚。现有数据表明，耐药表型的获得涉及细胞壁重组；已有文献记录了多效性变化，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酶敏感性的改变。然而，到目前为止，似乎不太可能用单一的机制或一系列机制来解释所有研究的临床糖肽耐药菌株的耐药性，因为还没有一致的表型或生化变化被发现。我们认为，耐药表型涉及多个基因变化。我们计划多管齐下研究耐药机制(S)。首先，有了四个金黄色葡萄球菌的完整基因组序列，我们将利用微阵列分析来比较GP敏感和耐药分离株中相关细胞壁代谢和两组分信号转导基因的表达模式。等基因、敏感和耐药的临床分离株对的可用性将为这一分析提供宝贵的工具。适当的上调和下调基因将作为进一步研究的目标，包括序列比较、Northern印迹分析、相关遗传背景下的等位基因失活和过度表达。这些研究将有助于理解金黄色葡萄球菌抵抗GPs杀菌作用的机制，并有望找到治疗耐药菌株感染的新思路。

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.