DNA gyrase and quinolone resistance in tuberculosis

描述（由申请人提供）：本项目的目的是了解喹诺酮类药物在分枝杆菌中的作用，并发现保护化合物免受耐药性发展的方法。先前的工作表明，氟喹诺酮类药物C-8位的结构修饰增加了抗菌活性，特别是对氟喹诺酮耐药突变体。这一特点，再加上氟喹诺酮结构的其他变化，将进行检查，以探讨致命的活动产生的部分从附着到裂解的DNA的促旋酶亚基的解离的假设。由于旋转酶亚基解离在蛋白质合成的情况下被测定为致死活性，因此这项工作可能揭示改善对非生长细菌的作用的方法。为了确定低氟喹诺酮浓度如何影响耐药性的发展，将检查通过在低药物浓度下选择性生长获得的结核分枝杆菌的非旋转酶耐药性突变体增加随后的旋转酶突变体选择性富集的频率的能力。预计研究的这一部分将影响氟喹诺酮给药策略。在患者中，M.结核病很容易产生耐药性，因此抗结核药物作为联合疗法给药;因此，将检测新的氟喹诺酮类药物与传统药物联合的致死活性，以鉴定不太可能具有内在干扰活性的化合物的组合。传统药物也将与C-8-甲氧基氟喹诺酮类药物在动态体外模型中联合使用，以检查药效学不匹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。为了给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20世纪90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。从这些体外研究中出现的原则可能普遍适用于氟喹诺酮类药物治疗的细菌感染;有关耐药性的想法也可能扩展到其他化合物，其中新生抗菌药物耐药性以渐进、逐步的方式发展。

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.