New understanding of LTA as a determinant of daptomycin susceptibility in VRE E. faecium

项目概要： 肠球菌是多重耐药医院获得性感染的主要原因-第一个E ESKAPE的缩写。大多数E.在主要中心的屎肠分离物是万古霉素抗性的（VRE）， 达托霉素通常是治疗的最后一线杀菌药物。不幸的是达托霉素 耐药性越来越普遍，并可能在治疗期间出现。在这里我们发现了一种新的 VRE的脆弱性似乎与膜锚定脂磷壁的产生有关， 酸（LTA）。自然发生的E。屎肠突变体在这一途径，分离自感染 泌尿道，表现出对达托霉素的过敏性，对这种关键药物的MIC低20倍。 我们开发的初步数据表明，这源于一个名为lafB的基因突变， 其编码一种酶，该酶产生直接前体糖肽， 建成当选择达托霉素敏感性野生型水平或更高水平的回复突变体时， 我们观察到lafB总是第一个突变回来，这表明它可能是显性的， 导致达托霉素耐药性的其他突变。如果是这样的话，抑制lafB将使 通过其他机制消除达托霉素耐药性的潜力，或至少防止这些耐药性， 在治疗过程中发生突变。以下建议概述了一套严格的 实验探索达托霉素敏感性的新决定因素。

Project summary: Enterococci are leading causes of multidrug resistant hospital acquired infection – the first E in the ESKAPE acronym. Most E. faecium isolates at major centers are vancomycin resistant (VRE), and daptomycin is often the last line bactericidal drug for treatment. Unfortunately, daptomycin resistance is increasingly common, and can arise during treatment. Here we discovered a new vulnerability of VRE that appears to be related to production of membrane anchored lipoteichoic acid (LTA). A naturally occurring E. faecium mutant in this pathway, isolated from an infected urinary tract, exhibited hypersusceptibility to daptomycin, with a 20-fold lower MIC to this key drug. We developed preliminary data to show that this stemmed from a mutation in a gene termed lafB, which encodes an enzyme that make the immediate precursor glycopeptide onto which LTA is built. When selecting for revertants to the wild type level of daptomycin susceptibility or greater, we observed that lafB was always the first to mutate back, indicating that it may be dominant to other mutations that result in daptomycin resistance. If so, inhibition of lafB would have the potential to undo daptomycin resistance by other mechanisms, or at minimum, prevent those mutations from arising during treatment. The following proposal outlines a rigorous set of experiments to explore this new determinant of daptomycin susceptibility.