Methicillin-resistant S. aureus (MRSA) constitutes approximately 50% of clinical S. aureus isolates and is most commonly the result of production of a mutated pencillin-binding protein, PBP2a, which is able to carry out essential cell wall synthesis functions while maintaining a low-affinity for nearly all beta-lactam antibiotics. Decreased susceptibility to glycopeptides, typically considered first-line MRSA agents, has also been documented. Interestingly, among MRSA isolates, an increase in beta-lactam susceptibility has been documented in the presence of declining lipo- and glycopeptide susceptibility. This phenomenon, termed the "seesaw effect" has been documented both in vitro and in vivo. In the era of increasing antimicrobial resistance and few new drugs to treat these organisms, this phenomenon may provide novel ways to use our current antimicrobials in a new, and more effective, manner.

中文翻译：

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金黄色葡萄球菌中糖肽和脂肽的敏感性降低，并产生“跷跷板效应”：利用后门打开了吗？

耐甲氧西林金黄色葡萄球菌（MRSA）约占临床金黄色葡萄球菌分离株的50％，最常见的是产生突变的pencillin结合蛋白PBP2a的结果，该蛋白能够执行基本的细胞壁合成功能，同时保持几乎所有β-内酰胺类抗生素都具有低亲和力 对糖肽的敏感性降低，通常被认为是一线MRSA药物，也有文献记载。有趣的是，在MRSA分离株中，已经证明在脂肽和糖肽敏感性降低的情况下，β-内酰胺敏感性增加。这种现象被称为“跷跷板效应”，已经在体外和体内得到了证明。在抗菌素耐药性不断提高且治疗这些生物的新药很少的时代，