Molecular basis of bacterial small-colony variants / Base moléculaire des variants à petites colonies chez les bactéries

细菌小菌落变体的分子基础/基础分子变体 à petites colonies chez les bactéries

• 批准号: RGPIN-2015-05916
• 负责人: Malouin, Francois
• 金额: $ 2.77万
• 依托单位: Université de Sherbrooke
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=613822
• 关键词: Molecular; basis; bacterial; small; colony

Staphylococcus aureus (SA) and antibiotic resistant methicillin-resistant SA (MRSA) often cause chronic and difficult-to-treat infections. SA/MRSA are able to generate Small-Colony Variants (SCVs), which have been linked to persistent infections. The ability of SA/MRSA to switch to SCVs and vice versa seems to be an integral part the infection process leading to persistence. Compared to their normal counterparts, bacterial SCVs produce high amounts of protective biofilms (extracellular matrix in which bacteria are embedded). SCVs also have a great ability to survive and persist within host cells, a property that protects them from the host immune response. The switch to SCVs also facilitates the development of antibiotic resistance making SA/MRSA infections even more difficult to treat. This research program aims to study the molecular basis of SCV formation. The specific objectives are to: 1) Investigate the molecular basis of SCV formation through whole-genome sequencing (DNA and RNA) of genetically-related “SA-SCV” pairs; 2) Investigate the molecular basis of antibiotic resistance development occurring through SCVs; 3) Study the impact of SCV formation on virulence and persistence in the mammalian host; and 4) Establish the molecular basis of future strategies targeting SCVs. In Objectives 1 and 2, genome and transcriptome alterations responsible for the SCV phenotype will be identified. We expect finding different paths leading to SCV formation since several phenotypic expressions exist. We will then use a variety of in vitro, cellular and animal models to investigate how the different molecular mechanisms of SCV formation impact on virulence and persistence in the host (Objective 3). Objective 4 will built on these results to investigate and establish the molecular basis of new approaches to control SCVs such as the development of vaccines specifically tailored to target intracellular SA. Chronic lung infection is the most common cause of morbidity and mortality in cystic fibrosis (CF) patients. SA/MRSA is overall the most frequently isolated pathogen from CF patients and SCVs contribute to the persistence of infection. Studies have demonstrated the deleterious effects of SCVs and of MRSA on CF in children and adults, respectively. SCVs are also involved in the persistence of other diseases like bovine mastitis. Milk production is an important industry in Canada. Total losses linked to mastitis in dairy herds are estimated at over $400 million per year and SA is the leading cause of bovine mastitis in Canada. No SA vaccine has shown protective efficacy to date, in part because of the inadequacy of the immune response to counteract intracellular forms of SA. With the understanding of the fundamental mechanisms explaining the formation of SCVs, this research program will help the future development of specific antibiotics or vaccines that prevent SCV formation and SA/MRSA persistence.

金黄色葡萄球菌(SA)和耐甲氧西林金黄色葡萄球菌(MRSA)经常导致慢性和难以治疗的感染。SA/MRSA能够产生与持续性感染有关的小群体变异(SCV)。金黄色葡萄球菌/耐甲氧西林金黄色葡萄球菌相互转换为SCV的能力似乎是导致持久性的感染过程的一个组成部分。与正常的细菌SCV相比，细菌SCV产生大量的保护性生物膜(嵌入细菌的细胞外基质)。SCV还具有在宿主细胞内生存和持续生存的强大能力，这一特性可以保护它们免受宿主免疫反应的影响。转向SCV还促进了抗生素耐药性的发展，使SA/MRSA感染更难治疗。 本研究项目旨在研究SCV形成的分子基础。 其具体目标是：1)通过对遗传相关的SA-SCV对进行全基因组测序(DNA和RNA)来研究SCV形成的分子基础；2)研究SCV通过SCV产生抗生素耐药性的分子基础；3)研究SCV形成对哺乳动物宿主毒力和持久性的影响；以及4)建立未来针对SCV的策略的分子基础。 在目标1和2中，将确定引起SCV表型的基因组和转录组改变。我们希望找到不同的途径导致SCV的形成，因为存在几个表型表达。然后，我们将使用各种体外、细胞和动物模型来研究SCV形成的不同分子机制如何影响宿主的毒力和持久性(目标3)。目标4将以这些结果为基础，研究和建立控制SCV的新方法的分子基础，例如开发专门针对细胞内SA的疫苗。 慢性肺部感染是囊性纤维化患者发病和死亡的最常见原因。耐甲氧西林金黄色葡萄球菌(SA/MRSA)是CF患者最常见的病原菌，而SCV是导致持续感染的原因之一。研究表明，SCV和MRSA分别对儿童和成人的CF有有害影响。SCV还与其他疾病的持续存在有关，如牛乳腺炎。牛奶生产是加拿大的一个重要产业。据估计，每年与奶牛乳房炎有关的总损失超过4亿美元，SA是加拿大奶牛乳房炎的主要原因。到目前为止，还没有SA疫苗显示出保护效果，部分原因是免疫反应不足以中和细胞内形式的SA。随着对SCV形成的基本机制的了解，这项研究计划将有助于未来特定抗生素或疫苗的开发，以防止SCV的形成和SA/MRSA的持久性。