Identification of factors that control Mycobacterium tuberculosis biofilm growth

描述（由申请人提供）：治疗结核病（TB）需要6至9个月的多药治疗方案。长期化疗的主要原因之一是结核分枝杆菌（结核的病原体）具有抵抗药物暴露的非凡能力。细菌在其自然栖息地的持久性部分是由于它们在称为生物膜的多细胞结构群落中生长而促进的。一些微生物病原体如假单胞菌、念珠菌或链球菌等慢性感染的持久性归因于它们在宿主体内形成生物膜的能力。因此，为了了解结核分枝杆菌对药物暴露的持久性，我们一直在体外生长模型中研究其生物膜的发展。我们的初步观察表明，病原菌的生物膜形成受环境和遗传因素的双重控制。通过评价结核分枝杆菌生物膜对利福平和异烟肼的耐受性，我们发现生物膜中大量杆菌对这两种抗生素都产生了表型耐药，而在浮游悬浮液中生长的细胞仍对这两种抗生素敏感。这一观察结果提出了一个基本问题，即这些顽固分子是如何在生物膜内发育的。回答这个问题的方法之一是了解结核分枝杆菌形成生物膜的分子基础。我建议研究控制结核分枝杆菌生物膜发育的环境和遗传因素。识别这些因素对于理解持久者的发展以及设计针对它们的合适策略非常有用。公共卫生相关性：由结核分枝杆菌引起的结核病每年在世界上造成近200万人死亡，需要6至9个月的强化化疗才能进行治疗。长期抵抗化疗的结核分枝杆菌是有效治疗结核病的关键障碍。在这个项目中，我们通过研究结核分枝杆菌在生物膜中的生长和发育来解决其持久性问题。生物膜是附着在表面的多细胞结构，具有比浮游培养明显更多的耐药持久性。

DESCRIPTION (provided by applicant): Treatment of tuberculosis (TB) requires multi-drug regimen for a period of 6 to 9 months. One of the primary reasons for a long-term chemotherapy is the extraordinary ability of Mycobacterium tuberculosis, the causative agent of TB, to survive against drug exposure. Persistence of bacteria in their natural habitat is, in part, facilitated by their growth in multicellular structured community called biofilms. Persistence of chronic infections by several microbial pathogens such as Pseudomonas spp., Candida spp. or Streptococcus spp. has been attributed to their ability to form biofilms inside host. Therefore, in order to understand the persistence of M. tuberculosis against drug exposure we have been studying the development of its biofilms in an in vitro growth model. Our preliminary observation suggests that the biofilm formation by pathogen is controlled by both environmental and genetic factors. Upon evaluation of tolerance properties of M. tuberculosis biofilms against rifampicin and isoniazid we found that a significantly large number of bacilli in biofilms developed phenotypic resistance against both the antibiotics, whereas cells growing in planktonic suspension remained susceptible. This observation raises a fundamental question as to how these persisters develop within biofilms. One of the approaches in answering this question will be to understand the molecular basis of biofilm development by M. tuberculosis. I propose to investigate the environmental and genetic factors that control the biofilm development of M. tuberculosis. Identification of such factors will be very useful in understanding the development of persisters as wells as designing suitable strategies to targeting them. PUBLIC HEALTH RELEVANCE: Tuberculosis (TB), caused by Mycobacterium tuberculosis, kills nearly 2 million people in the world every year and takes 6 to 9 months of intensive chemotherapy for the treatment. Long-term persistence of M. tuberculosis against chemotherapy is a key hurdle in an effective treatment of TB. In this project we are addressing the persistence issue of M. tuberculosis by studying its growth and development in biofilms- the surface attached multicellular structures with significantly more drug tolerant persisters than planktonic cultures.