Pathogenesis of multi drug-resistant and extensively drug-resistant tuberculosis as a determinant of future treatment success.
Pathogenesis of multi drug-resistant and extensively drug-resistant tuberculosis as a determinant of future treatment success.
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多重耐药和广泛耐药结核病的发病机制是未来治疗成功的决定因素。
DOI：
10.1016/j.ijmyco.2016.11.017
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发表时间：
2016
影响因子：
1.2
通讯作者：
Valafar,Faramarz
中科院分区：
文献类型：
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作者：
Valafar,Faramarz
方法对来自印度、菲律宾、摩尔多瓦、南非和瑞典5个国家的385株临床结核分枝杆菌（多数为XDR）进行研究。全基因组测序在Pacific Biosciences (1380 Willow Road, Menlo Pak, CA 94025， USA) RS I和II平台上进行。所有分离株均在分枝杆菌生长指示管（MGIT; MGIT960; Bactec, Becton, Dickinson and Company, 1 Becton Drive, Franklin Lakes, New Jersey 07417-1880， USA）上进行8种一线和二线药物的药敏试验。鉴定了每种分离物对每种药物的耐药机制，并将其定位到分离物的地理起源。全基因组系统基因组学用于祖先重建。研究了克隆性以确定暴发，并将其用作衡量毒力的替代指标。还研究了MGIT的生长曲线，以估计适应度。结果一些耐药机制似乎具有区域特异性。在来自印度和南非的MDR和XDR分离株中发现了一些克隆扩增。生长曲线分析确定了两个不同的过程。第一个过程的增长率较低，几天后会消退，但它主要推动最初几天的增长。第二个过程的生长速度明显更高，并且在几天后开始（或在最初几天内具有不可测量的生长速度），并且在孵化的最初几天后驱动全部或大部分生长。我们观察到的分离株似乎很晚才开始第二阶段，或者根本没有开始。对一个区域的耐药性机制的特异性是一个非常值得关注的问题，也是一个尚未得到很好理解的现象。然而，它清楚地表明了进化途径的多样性，以达到表型抗性状态。进化的过去是进化轨迹的决定因素；因此，令人担忧的是，细菌将继续在世界不同地区以不同的方式进化，因此需要不同的治疗策略。在这种情况下，结核病的标准全球治疗将不得不放弃。缺失（或延迟）的二次生长过程也是一个严重的问题，因为它允许细菌逃避基于生长的表型检测。这是世界卫生组织的建议，也是确定耐药性的最普遍方法；因此，这种逃避无疑是实现耐多药/广泛耐药状态的途径，并破坏全球结核病控制。这些耐药分离株将被标记为“易感”，并将继续进行标准治疗，从而为产生额外耐药性提供时间。MDR/XDR细菌的克隆扩增显然消除了高耐药分离株不适合或毒性较差的观念。这个因素可能对某些细菌是正确的；然而，我们也发现了许多相反的证据。这一发现表明不同的微进化导致不同的适合度和毒力。
MethodsWe studied 385 (mostly XDR) clinical Mycobacterium tuberculosis isolates from five countries: India, the Philippines, Moldova, South Africa, and Sweden. Whole genome sequencing was performed on Pacific Biosciences (1380 Willow Road, Menlo Pak, CA 94025, USA) RS I and II platforms. Drug susceptibility testing for eight first-and second-line drugs was performed on mycobacteria growth indicator tubes (MGIT)(MGIT960; Bactec, Becton, Dickinson and Company, 1 Becton Drive, Franklin Lakes, New Jersey 07417-1880, USA) for all isolates. Each isolate's mechanisms of resistance to each drug was identified and mapped to the geographic origin of the isolate. Genome-wide phylogenomics was used for ancestral reconstruction. Clonality was studied to identify outbreaks and used as a proxy for measuring virulence. Growth curves in MGIT were also studied for the estimation of fitness.ResultsSome mechanisms of resistance seem to be region-specific. Several clonal expansions were identified among the MDR and XDR isolates from India and South Africa. Growth curve analysis identified two distinct processes. The first process has a lower growth rate and subsides after a few days, but it predominantly drives the growth in the initial days. The second process has a distinctly higher growth rate and begins a few days later (or has an immeasurable growth rate in the first few days) and drives all or most of the growth after the first few days of incubation. We observed isolates that seemed to start their second phase very late or not at all.DiscussionSpecificity of a mechanism of resistance to a region is a great concern and a phenomenon that is not well understood. However, it is a clear indication of the multiplicity of an evolutionary path to a phenotypic resistance state. The evolutionary past is a determinant of the evolutionary trajectory; therefore, the concern is that bacteria will continue to evolve differentially in different regions of the world and hence will require different treatment strategies. In such a scenario, a standard global treatment of TB will have to be abandoned. The missing (or delayed) secondary growth process is also of grave concern because it allows the bacterium to escape growth-based phenotypic detection. This is the World Health Organization's recommendation, and most prevalent method, for determining resistance; therefore, this escape undoubtedly is a path to achieving an MDR/XDR state and undermines global TB control. Such resistant isolates would be labeled as “susceptible” and standard treatment would continue, and thereby provide time for the development of additional resistance. The clonal expansion of MDR/XDR bacteria clearly dispels the notion that highly resistant isolates are less fit or virulent. This factor may be true for some bacteria; however, we also found much contradicting evidence. This finding indicates differential microevolution and results in differential fitness and virulence.