Fitness Cost and Compensation in Quinolone-Resistant Mycobacterium tuberculosis

描述(申请人提供)：正在进行临床试验，以评估氟喹诺酮类药物缩短标准结核病治疗的潜力，并正在开发新的氟喹诺酮类化合物，旨在提高抗结核分枝杆菌的特异性和活性。耐药性的出现是对这类新的抗结核药物成功的最大威胁。理论和实验数据表明，这一过程将受到细菌适应性差异的显著影响。我们最近发现，耐利福平结核分枝杆菌的竞争适合度取决于特定的耐药突变和菌株遗传背景，竞争适合度实验可以预测临床环境中耐药的流行病学。在这里，我们打算探索氟喹诺酮类药物中的这些现象。我们将在两个不同的菌株背景下产生自发的氟喹诺酮耐药菌株，并测量它们的竞争适应性。我们将把这些适合度测量与临床氟喹诺酮耐药菌株集合中相应耐药等位基因的频率进行比较，我们将通过国际合作汇编这些菌株。我们将实验性地进化一些氟喹诺酮耐药突变以允许补偿，并使用比较的全基因组重测序来识别假定的补偿突变。这些假定的补偿性突变将在我们的临床氟喹诺酮耐药菌株集合中得到验证，作为对照，将在我们代表全球结核分枝杆菌系统发育多样性的泛敏感菌株集合中得到验证。该项目是朝着更好地了解结核分枝杆菌对氟喹诺酮类药物耐药性的生态学迈出的第一步，对结核病控制和药物开发具有潜在的重要影响。随后的工作将能够确定适应性差异和补偿的分子基础。结核病的治疗迫切需要新药。一类新的抗菌药，氟喹诺酮类，是目前正在研究的有希望的候选药物。然而，对这些新药的耐药性很可能会出现。为了最大限度地提高结核病控制的效益，迫切需要更好地了解影响氟喹诺酮类药物耐药性的细菌因素。

DESCRIPTION (provided by applicant): Clinical trials are underway to evaluate the potential of fluoroquinolones to shorten the standard tuberculosis treatment, and new fluoroquinolone derivatives are being developed aiming at higher specificity and activity against Mycobacterium tuberculosis. The emergence of drug resistance represents the most significant threat to the success of this new class of anti-tuberculosis agents. Theoretical and experimental data suggest that this process will significantly be influenced by differences in bacterial fitness. We recently showed that the competitive fitness of rifampin-resistant M. tuberculosis depends on the specific resistance-conferring mutation and strain genetic background, and that competitive fitness experiments are predicative of the epidemiology of drug resistance in clinical settings. Here we propose to explore these phenomena in fluoroquinolones. We will generate spontaneous fluoroquinolone-resistant strains in two different strain backgrounds and measure their competitive fitness. We will compare these fitness measurements to the frequency of the corresponding resistance alleles in a collection of clinical fluoroquinolone-resistant strains, which we will compile through our international collaborations. We will experimentally evolve some of the fluoroquinolone- resistant mutants to allow for compensation, and use comparative whole-genome resequencing to identify putative compensatory mutations. These putative compensatory mutations will be validated in our collection of clinical fluoroquinolone-resistant strains and, as a control, in our collection of pan-susceptible strains representative of the global phylogenetic diversity of M. tuberculosis. This project represents a first step towards a better understanding of the ecology of fluoroquinolone resistance in M. tuberculosis, with potentially important implications for tuberculosis control and drug development. Subsequent work will then be able to identify the molecular basis of fitness differences and compensation. New drugs are urgently needed for the treatment of tuberculosis. A new class of antimicrobials, the fluoroquinolones, are promising candidates that are currently being investigated. However, resistance to these new drugs is likely to emerge. In order to maximize the benefit for tuberculosis control, there is an urgent need to better understand the bacterial factors that influence resistance to fluoroquinolones.