DNA gyrase and quinolone resistance in tuberculosis

描述(由申请人提供)：该计划的目标是了解喹诺酮类药物如何在分枝杆菌中发挥作用，并发现保护化合物免受耐药性发展的方法。以前的工作表明，氟喹诺酮类药物C-8位的结构修饰可以提高抗菌活性，特别是对氟喹诺酮类耐药突变株。这一特征，加上氟喹诺酮结构的其他变化，将被研究以探索这一假设，即致死活性部分来自于连接到切割的DNA上的旋转酶亚基的解离。由于在没有蛋白质合成的情况下，旋转酶亚单位的解离被认为是致命的活性，这项工作可能会揭示出改善对不生长的细菌的作用的方法。为了确定低氟喹诺酮类药物浓度如何影响耐药性的发展，将检测通过在低药物浓度下选择性生长获得的结核分枝杆菌非旋转酶耐药突变株，以了解它们是否有能力增加随后的旋转酶突变株选择性浓缩的频率。这部分研究预计将影响氟喹诺酮类药物的给药策略。在患者中，结核分枝杆菌很容易产生耐药性，以至于抗结核药物被作为联合疗法使用；因此，将结合传统药物检查新的氟喹诺酮类药物的致死活性，以确定不太可能具有内在干扰活性的化合物组合。传统药物还将与C-8-甲氧基氟喹诺酮类药物在体外动态模型中结合，以检查药效失配对耐药性发展的影响。该计划的这两个方面将有助于优化新氟喹诺酮类药物的使用。为了为这项工作提供临床背景，将检查来自纽约市的分离株对氟喹诺酮类药物的敏感性。将1990年代初获得的分离株与最近获得的分离株进行比较，将表明敏感性是否正在丧失。从这些体外研究中得出的原理可能普遍适用于需要氟喹诺酮类药物治疗的细菌感染；关于耐药性的想法也可能延伸到其他化合物，在这些化合物中，从头开始的抗菌素耐药性是逐步发展的。

DESCRIPTION (provided by applicant): The goals of this program are to understand how the quinolones act in mycobacteria and to discover ways to protect the compounds from the development of resistance. Previous work showed that structure modifications at the C-8 position of fluoroquinolones increase antibacterial activity, particularly with fluoroquinolone-resistant mutants. This feature, plus other variations in fluoroquinolone structure, will be examined to explore the hypothesis that lethal activity arises in part from the dissociation of gyrase subunits attached to cleaved DNA. Since gyrase subunit dissociation is assayed as lethal activity in the absence of protein synthesis, this work may reveal ways to improve action against nongrowing bacteria. To define how low fluoroquinolone concentrations affect the development of resistance, non-gyrase resistance mutants of Mycobacterium tuberculosis, obtained through selective growth at low drug concentration, will be examined for their ability to increase the frequency at which subsequent gyrase mutants are selectively enriched. This portion of the study is expected to influence fluoroquinolone dosing strategies. In patients, M. tuberculosis develops resistance so readily that anti-tuberculosis agents are administered as combination therapies; consequently, the lethal activity of new fluoroquinolones will be examined in combination with traditional agents to identify combinations of compounds that are unlikely to have intrinsic interfering activities. Traditional agents will also be combined with C-8-methoxy fluoroquinolones in a dynamic in vitro model to examine the effect of pharmacodynamic mismatch on the development of resistance. These two aspects of the program will help optimize the use of new fluoroquinolones. To provide a clinical context for the work, isolates from New York City will be examined for susceptibility to fluoroquinolones. Comparison of isolates obtained in the early 1990s with those obtained recently will indicate whether susceptibility is being lost. Principles emerging from these in vitro studies may be generally applicable to bacterial infections for which fluoroquinolone treatment is indicated; ideas concerning resistance may also extend to other compounds in which de novo antimicrobial resistance develops in a gradual, stepwise manner.