Susceptibility of Mycobacterium tuberculosis clinical isolates to moxifloxacin

描述（由申请人提供）：背景：莫西沙星是一种新一代喹诺酮类药物，目前正在进行临床试验评估，以用作一线抗结核药物。人类和动物数据表明，各种喹诺酮类药物之间存在交叉耐药性，结核分枝杆菌（MTB）分离株的喹诺酮耐药性可能影响治疗效果。目前还没有发表的关于一般人群中MTB临床分离株对阿托沙星或其他喹诺酮类药物耐药的流行率的系统分析。此外，数据表明，gyrA基因的QRDR区域中的突变仅占MTB分离株中喹诺酮类药物耐药性的42-85%，这表明QRDR以外或其他基因中的突变在MTB的喹诺酮类耐药性中起作用。具体目标：1）分析24个月内来自哈里斯县休斯顿的MTB临床分离株中对阿托沙星、左氧氟沙星和氧氟沙星的敏感性降低的MTB菌株的患病率，以及2）鉴定与对所研究的喹诺酮类药物的敏感性降低相关的gyrA、gyrB和Rv 2686 c-Rv 2687 c-Rv 2688 c基因中的突变。研究方法：作为该市结核病控制工作的一部分，来自哈里斯县休斯顿的>95%的MTB临床分离株被送往德克萨斯州卫生服务部。我们将使用琼脂比例间接药敏法，前瞻性检测24个月内所有结核分枝杆菌临床分离株对异烟肼、利福平、乙胺丁醇、氧氟沙星、左氧氟沙星和利多卡因的耐药性。我们将从对喹诺酮类药物敏感性降低的MTB分离株和匹配数量的喹诺酮类药物敏感分离株中提取DNA，以比较gyrA、gyrB和Rv 2686 c-Rv 2687 c-Rv 2688 c基因的序列;这些基因在喹诺酮类药物敏感性中具有推定或证实的作用。结果/数据：研究结果将作为结核分枝杆菌对利多卡因耐药的流行率及其与一线抗结核药物和其他喹诺酮类药物耐药的相关性的数据。将鉴定MTB中与喹诺酮耐药相关的突变。这些数据将代表第一次全面分析结核分枝杆菌分离株中喹诺酮类药物耐药性的流行情况及其在一般人群中的遗传机制。2005年10月，结核病联盟（全球结核病药物开发联盟）和拜耳制药公司宣布计划在临床试验中研究阿托沙星，旨在缩短结核病治疗方案的时间，经过几十年的结核病药物开发极其缓慢。结核病对阿托沙星的耐药性可能会降低其纳入结核病药物治疗方案的有效性，医学文献缺乏关于结核分枝杆菌（MTB）对阿托沙星耐药性普遍程度的系统性数据。我们计划系统研究24个月内从哈里斯县休斯顿患者中收集的结核分枝杆菌菌株中对氟沙星耐药的流行情况，从而提供可用作帮助设计更好的治疗方案的数据，并为未来监测和研究结核分枝杆菌喹诺酮类药物耐药性提供基础。

DESCRIPTION (provided by applicant): Background: Moxifloxacin, a later-generation quinolone, is currently undergoing evaluation in clinical trials for use as first-line antituberculous agent. Human and animal data suggest that there is cross resistance among various quinolones and that quinolone-resistance in Mycobacterium tuberculosis (MTB) isolates can affect the efficacy of the treatment. There are no published systematic analyses of the prevalence of resistance to moxifloxacin or other quinolones in MTB clinical isolates in the general population. Moreover, data suggest that mutations in the QRDR region of the gyrA gene account for only 42-85% of quinolone drug resistance in MTB isolates, suggesting that mutations outside the QRDR or in other genes play a role in quinolone resistance in MTB. Specific Aims: 1) To analyze the prevalence of MTB strains with reduced susceptibility to moxifloxacin, levofloxacin and ofloxacin in MTB clinical isolates from Houston, Harris County over 24 months and 2) To identify mutations in the gyrA, gyrB and Rv2686c- Rv2687c-Rv2688c genes that are associated with reduced susceptibility to the studied quinolones. Methods: As part of the tuberculosis control efforts in the city, >95% of MTB clinical isolates from Houston, Harris County are sent to the Texas State Department of Health Services. We will prospectively test all MTB clinical isolates for resistance to isoniazid, rifampin, ethambutol, ofloxacin, levofloxacin and moxifloxacin over a 24-month period, using the agar proportion indirect susceptibility method. We will extract the DNA from MTB isolates with reduced susceptibility to quinolones and a matched number of quinolone susceptible isolates to compare the sequences of the gyrA, gyrB and Rv2686c-Rv2687c-Rv2688c genes; genes of putative or demonstrated role in susceptibility to quinolones. Results/data: The study results will be presented as data on the prevalence of MTB moxifloxacin resistance and its correlation with resistance to first-line anti-TB drugs and other quinolones. Mutations associated with quinolone resistance in MTB will be identified. The data will represent the first comprehensive analysis of the prevalence of quinolone drug resistance in MTB isolates and its genetic mechanisms in the general population. In October 2005, TB Alliance (Global Alliance for tuberculosis (TB) drug development) and Bayer Pharmaceuticals announced plans to study moxifloxacin in clinical trials aiming at shortening the length of TB treatment regimens, after decades of exceedingly slow TB drug development. Resistance to moxifloxacin in TB can potentially reduce the effectiveness of its inclusion in TB drug regimens, and the medical literature lacks systemic data on how prevalent moxifloxacin resistance in Mycobacterium tuberculosis (MTB) is. We propose to systematically study the prevalence of moxifloxacin drug resistance in MTB strains collected from patients in Houston, Harris County over a period of 24 months, thus providing data that can be used as a too to help design better treatment regimens and provide the basis for future monitoring and research on the topic of quinolone drug resistance in MTB.