Dissecting an antibiotic resistance network in the hospital 'superbug' Enterococcus faecalis

医院获得性肠球菌感染对公共卫生造成了重大负担，英国每年报告的菌血症病例约为5000例，估计死亡率为20%。肠球菌是人体肠道微生物区系的天然组成部分。感染通常发生在患者因无关感染而接受治疗后，这是因为肠球菌具有惊人的内在耐药性。虽然接受抗生素治疗的患者体内的大多数细菌都会死亡，但肠球菌往往会茁壮成长，这反过来又会大幅增加肠球菌感染的风险。过去对肠球菌耐药性的研究主要集中在抗生素万古霉素，它是治疗此类感染的常用药物，我们现在对其具体的耐药机制有了很好的了解。然而，令人惊讶的是，我们对细菌对许多其他抗生素产生内在耐药性的分子基础知之甚少。考虑到这种普通耐药性为肠球菌提供了致病的机会，解决这个问题是及时和高度相关的。这个学生项目旨在获得分子和系统水平的了解粪肠球菌对靶向细胞膜的抗生素的反应。在格哈德实验室以前工作和文献的基础上，候选人将确定候选调节器和抗性基因，并通过实验研究控制粪肠球菌细胞膜应激反应的信号通路。为了最大限度地提高成功率并确定完整的调控网络，学生将采用随机和定向突变相结合的双管齐下的方法。候选调节者将通过失去靶基因调控和抗性来确认。我们最近已经证明，抗生素耐药性可以在复杂的分层网络中组织起来，该网络利用单个耐药性决定因素S之间的活跃程度来补偿单个组件的故障。因此，学生将使用生物化学、遗传学和数学模型来分析任何确定的跨沟通和层级组织的调节因素。监督小组的广泛专业知识将确保对应聘者进行实践和理论上最先进的方法的交叉培训。对粪肠球菌抗生素应激反应的系统水平组织的详细了解可能最终允许识别可用于开发靶向治疗策略的阿喀琉斯之踵。与丹麦的一个临床医生团队建立了联系，他们可以测试研究结果的相关性，例如通过检查他们的流行病学数据的流行率和关键调控因子中潜在的病理适应性突变，这将提供这项研究在临床上的立即应用。

Hospital-acquired infections with Enterococcus bacteria impose a significant public health burden, with ca. 5000cases of bacteraemia reported in the UK each year and an estimated mortality rate of 20%. Enterococci form anatural component of the human gut microflora. Infections usually arise following treatment of a patient for anunrelated infection, and this is because enterococci possess a striking degree of intrinsic drug resistance. While mostbacteria within a patient receiving antibiotics die, enterococci can often thrive, which in turn sharply increases the riskfor enterococcal infections. Past studies of drug resistance in enterococci have mostly focussed on the antibioticvancomycin, which is commonly used to treat such infections, and we now have an excellent understanding of thespecific resistance mechanisms involved. However, we know surprisingly little about the molecular basis for theintrinsic resistance of the bacteria against many other antibiotics. Considering that this generic resistance is whatprovides enterococci with the opportunity to cause disease, addressing this question is timely and highly relevant.This studentship project is aimed at gaining a molecular and systems level understanding of the response ofEnterococcus faecalis to antibiotics that target the cell envelope. Building on previous work from the Gebhard lab andthe literature, the candidate will identify candidate regulators and resistance genes, and experimentally investigatethe signalling pathways that control the cell envelope stress response of E. faecalis. To maximise success andidentify the complete regulatory network, the student will apply a two-pronged approach combining random andtargeted mutagenesis. Candidate regulators will be confirmed by loss of target gene regulation and resistance. Wehave recently shown that antibiotic resistance can be organised in complex hierarchical networks that utilise activeredundancy between individual resistance determinant s to compensate for failure of individual components. Thestudent will therefore analyse any identified regulators for cross-communication and hierarchical organisation usingbiochemistry, genetics and mathematical modelling. The broad expertise of the supervisory team will ensure crosscuttingtraining for the candidate in both practical and theoretical state-of-the-art methodology. A detailedunderstanding of the systems level organisation of the antibiotic stress response of E. faecalis may ultimately allowthe identification of an Achilles' heel that can be exploited for the development of targeted therapeutic strategies.Contacts are in place to a team of clinicians in Denmark who can test the relevance of the findings, e.g. by examiningtheir epidemiological data for prevalence and potential pathoadaptive mutations in the key regulators, which willprovide immediate application of this study in a clinical context.