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

项目总结： 肠球菌是耐多药医院获得性感染的主要原因-第一个E ESKAPE的首字母缩写。主要中心的大多数粪肠球菌对万古霉素耐药(VRE)， 而达托霉素往往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，在治疗过程中可能会出现耐药性。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酸的产生有关 酸(LTA)。粪肠球菌在此途径中自然产生的粪肠球菌突变体，从受感染的 尿路，对达托霉素表现出过敏反应，对这种关键药物的MIC降低20倍。 我们开发的初步数据表明，这源于一种名为LAFB的基因的突变， 它编码一种酶，生成LTA所在的直接前体糖肽 建好了。当选择回复株至野生型达托霉素敏感性水平或更高时， 我们观察到LAFB总是最先突变回来的，这表明它可能对 其他导致达托霉素耐药的突变。如果是这样的话，抑制LAFB将具有 有可能通过其他机制消除对达托霉素的耐药性，或至少防止 在治疗过程中产生的突变。下面的提案概述了一套严格的 探索这种新的达托霉素敏感性决定因素的实验。

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.