【作者】 杨本付；

【导师】 姜庆五；

【作者基本信息】 复旦大学 ， 流行病与卫生统计学， 2004， 博士

【摘要】 由于流动人口骤增,艾滋病流行,耐药结核病蔓延,发展中国家贫穷加剧和对结核病控制的忽视等,全球结核病疫情再次恶化。我国结核病疫情加重的突出原因是耐药结核病的广泛流行,进入90年代后,我国结核病仍然以高耐药率为特点,被WHO/IUATLD列为MDR-TB的“热点”之一。目前我国农村集中了80%的TB病人,是耐药TB防制研究的重点。本研究运用WHO/IUATLD推荐的比例法药敏试验测定苏北农村两县2002年的初治和复治TB病人的初始分离株对四种一线抗痨药的敏感性,进行耐药谱分析;在定性研究的基础上,设计调查表,深入探讨农村耐药TB的影响因素;用PCR-SSCP检测利福平耐药菌株的rpoB基因突变,以PCR-RFLP检测INH耐药菌株的katG S315T突变,进一步揭示INH耐药和RIF耐药的分子机制。此外,本文尝试运用VNTR分型方法研究了现场M.TB分离株的分子特征,分析了与VNTR基因型成簇的相关因素。研究结果如下:1. 定性研究表明,临床治疗结核病失败与结核病诊断和治疗过程中的人为因素有关,病人延误就医、对结核病治疗的依从性差在非项目县更加突出;老年病人由于年龄大、就诊不方便以及依靠子女赡养、经济状况欠佳等原因,就诊延误时间长,对结核病治疗的依从性相对较差。由于宣教开展不够,人们的结核病知识减少或缺乏,从而导致误诊、延误诊断、滥用抗生素、不规则治疗和治疗时间延长,这些均是可能滋生耐药性的重要因素。2. 药敏测定结果表明,当地总耐药率为32.9%,其中初始耐药率为28.6%,获得性耐药率为48.5%。同时耐STR和INH(31人)是最常见的耐两药或多药类型,其次是耐INH和RIF(26人)。四种抗结核药物的耐药率顺位依次为:INH(26.3%)、STR(24.3%)、RIF(18.4%)、EMB(10.5%)。同时对INH和RIF耐药的耐多药(MDR)率为17.1%,其中初始MDR率为16.0%,获得性MDR率为21.2%。28株RIF耐药株中,有26株同时耐INH,占92.9%,支持RIF耐药可作为MDR-TB标志的观点。本研究现场属于WHO/IUATLD定义的MDR-TB“热点”地区。3. 在苏北农村与耐药性有关的独立危险因素包括,来自非项目县、TB治疗史、不重视自身健康、就医延误1个月以上。男性一般有较高的耐药率水平,最年轻组和最年老组耐药率低,病人患有慢性病反而不易耐药。TB控制项目在防<WP=8>止耐药性发生中起到了积极的作用,但即使DOTS计划运作良好,耐药TB对治疗结果仍有严重的负面影响,表现为有一定的传播机会。本研究初治病例耐药率和MDR率均高,说明即使在项目县,也可能存在耐药株的传播。4. 两县的RIF耐药菌株的rpoB基因突变发生率平均为71.4%,敏感株均无突变。编码RNA聚合酶(亚单位的rpoB基因发生突变是M.TB耐RIF的主要分子机制。当地47.5%的INH耐药菌株存在katG S315T基因突变,其中复治病例为66.7%,初治病例为39.3%(P<0.05),没有发现katG基因缺失,INH敏感株中不存在该突变。katG S315T突变是INH耐药的主要机制之一。katG S315T突变的INH耐药菌株中MDR的比例为68.4%,无该突变菌株为61.9%。5. VNTR方法可以把研究现场的菌株分为不同的菌群。当地菌株VNTR类型成簇率高,优势类型VNTR 42435占菌株总数的38.6%,提示北京菌株在当地流行水平较高。尽管没有显著性,但具有下列因素的病例,其分离株VNTR类型成簇率较高:涂阳、非项目县、初治、年轻、BCG接种。INH耐药菌株成簇的可能性反而小,表明INH耐药株的传播性和致病性可能下降,但katG S315T突变的INH耐药株的致病性并未下降,成簇率高于INH敏感株。VNTR 42435与BCG接种联系不显著,可能不支持BCG造成菌株选择性压力的观点。VNTR 42435类型与耐四种药的联系均未达到显著性,尚不能认为其优势来自对某些抗痨药的耐药。上述研究结果提示:⑴ 当地农村耐药结核病疫情严重,耐药性的发生趋向于对多种药物同时耐药,尤其是同时对INH和RIF耐药。与耐药性有关的因素包括,来自非项目县、TB治疗史、不重视自身健康、就医延误1个月以上;⑵ 当地农村医务人员仍需进一步培训提高,重点规范结核病的诊治过程,着眼于对病人及其家属进行教育的技能。加强DOTS项目的实施有助于减少耐药结核病的发生和传播;⑶ rpoB基因突变在当地可以成功地用作RIF耐药M.TB菌株快速检测的遗传学标志。以256 bp的rpoB基因片段进行SSCP分析的特异度为100%,灵敏度为71.4%;⑷ 有katG S315T基因突变的M.TB临床分离株仍有致病性,且容易获得对其他抗痨药的耐药。在当地katG S315T突变流行率较高的情况下,不应忽视INH耐药的防治。katG S315T突变在当地可用作M.TB分离株INH耐药快速检测的一种可靠标志;⑸ VNTR分型方法简单快速、分型结果数字化,可以把菌株分为不同的菌株群,用于研究菌株的种群结构和分子流行病学。由于本研究样本量有限,有必要扩大样本进一步研究证实和解释本文的结果。更多还原

【Abstract】 Tuberculosis (TB) reemergence and spread are of worldwide concern, which is largely due to substantial levels of migration of people, increasing circulation of drug-resistant TB, HIV/AIDS epidemic and neglect of national tuberculosis program. Widespread of drug-resistant tuberculosis is considered an important factor of resurgence of TB in China. During the last decade, TB in China has remained a high drug-resistance rate, which renders China one of the hotspots of MDR-TB according to WHO/IUATLD drug-resistance surveillance project. Rural area is home to about eighty percent of TB patients in China at present time, extensive investigation on drug-resistant tuberculosis is urgent at these sites.We determined the susceptibility of four first-line anti-tuberculosis drugs for initial isolates from both new and previously treated TB cases from 2 counties in north Jiangsu province by standardized proportion method. The profile of resistance to all the four drugs were analysed. We conducted an extensive survey on determinants of drug-resistant tuberculosis in rural area using a questionnaire designed on the basis of the previous qualitative study. To further understand the molecular mechanism of drug resistance, a PCR-SSCP assay was used to detect mutations in rpoB gene confering resistance to RIF, and a PCR-RFLP assay to detect a particular substitution in codon 315 (katG S315T), which is associated with INH resistance. Also, we tried to use VNTR typing to characterize M.TB isolates from the study sites, analysed the factors for VNTR clustering. The results are as follows.1. The qualitative study showed that the failure of treatment of tuberculosis is associated with man-made factors in the course of diagnosis and treatment of tuberculosis. Delay in health seeking, poor compliance to treatment is a problem in the county without DOTS program. Aged TB patients generally have longer delay time in health seeking and poor compliance to treatment regimens because of age, disability and bad economic status. Limited health education and propagand about TB led to misdiagnosis, delay in diagnosis, abuse of antibiotics, irregular treatment and a prolonged period of treatment. All of these are possible factors of drug-resistance. <WP=10>2. Drug susceptibility testing (DST) showed that, among the 152 patients with DST results, 32.9% were resistant to at least one of the first-line anti-tuberculosis drugs. Initial and acquired drug resistance rate were 28.6% and 48.5%, respectively. Resistance to STR and INH (31 cases) is the most common resistance pattern. Resistance rate to INH, STR, RIF and EMB is 26.3%, 24.3%, 18.4% and 10.5%, successively. 17.1% were resistant to both INH and RIF (MDR). Of the 28 RIF resistant isolates 26 (92.9%) were resistant to INH,supporting the idea of using RIF resistance as a surrogate marker for MDR-TB. These study sites should be a hotspot of MDR-TB according to WHO/IUATLD.3. Determinants of drug-resistance in rural north Jiangsu province included, previous treatment for TB, residence in the county without DOTS program, indifference to their health condition and delay in health seeking for more than 1 month. Male patients have a higher resistance rate, and both the youngest and eldest patients have lower rates of resistance. Patients suffering from chronic disease also have lower drug resistance rate. Tuberculosis control program have positive impact on preventing drug-resistance. In the context of a well-functioning DOTS program, drug-resistant TB still has a profoundly adverse impact on treatment outcome. Drug resistance rate and MDR rate are both high in new TB cases, indicating some possible transmission of drug-resistant strains even in the county with DOTS program.4. The overall prevalence of muations in rpoB gene of RIF-resistant strains from the two counties is 71.4%. No mutations were detected in the RIF-susceptible strains. Rifampin resistance arises due to mutations in rpoB gene encoding the DNA-dependent RNA polymerase. 47.5% of the INH-resistant strains have katG S315T substit更多还原