Diet driven evolution of epidemic ribotypes of Clostridium difficile

导致发病率和死亡率增加的病原体的出现是一个重大的公共卫生问题 关心艰难梭菌是医院获得性感染的主要原因，并且是导致感染的主要原因。 腹泻相关性腹泻。在过去的十年中，两个流行的核糖体型（RT 027和RT 078）的C。艰难 在世界各地的医院爆发中， 2000年前的水平。这些核糖体类型与发病率和死亡率的增加有关 并被归类为高毒性然而，为什么这些菌株开始 在2000年代初出现的情况尚不清楚。 我们已经发现RT 027和RT 078菌株已经获得了在二糖上生长的能力 海藻糖比其他核糖型C.很难我们的初步数据显示， 在这两种核糖体类型中改善生长的基础在遗传和机制上是不同的，这表明 在这些遗传学上不同的核糖型中改进的海藻糖代谢的趋同进化。此外，本发明还提供了一种方法， 我们发现，破坏RT 027菌株利用海藻糖的能力可显著减弱疾病 严重性，表明海藻糖代谢有助于RT 027和RT 078的高毒力性质 菌株海藻糖是葡萄糖的一种双糖，在获得批准后成为一种广泛使用的食品补充剂 2000年获得FDA GRAS认证，2001年获得欧洲EFSA认证。海藻糖具有许多令人期望的 由于α，α 1-1键是热和酸稳定的，这使得它具有作为糖添加剂的性质， 甜度比蔗糖低45%。海藻糖通常存在于蘑菇和贝类等食物中， 添加到从碎牛肉到冰淇淋的许多食品和饮料产品中。 海藻糖在全球食品供应中的添加与RT 027的首次报告一致， RT 078菌株在21世纪初，即使这些核糖体早在1985年就存在于医院。 我们建议，在食品供应中增加海藻糖的水平已经选择了RT 027， RT 078菌株由于其能够更有效地代谢海藻糖， 流行病我们将在我们的实验室中使用两个最近开发的模型，人类粪便微型生物反应器阵列 模型C.艰难梭菌侵袭和人源化的C.艰难梭菌感染，研究 海藻糖和改进的海藻糖代谢对RT 027和RT 078菌株引起C. 艰难感染我们还将研究RT 027改善海藻糖代谢的机制基础 和RT 078菌株。最后，我们将评估改善海藻糖代谢对定植的影响 动态，疾病的严重程度和携带这些高毒力的C. difficile ribotypes。以下 具体目标如下：目标1。探讨了C. difficile增加疾病的严重程度。目标2.了解改良海藻糖的机理基础 RT027 C.很难目标3。了解获得性海藻糖操纵子在 RT 078健身和动物车。我们希望这项工作将建立最近增加的 人类饮食中的海藻糖和流行性C. difficile ribotypes。这将提供第一个 人类饮食改变直接影响肠道感染发病机制的直接证据。

The emergence of pathogens that cause increased morbidity and mortality is a major public health concern. Clostridium difficile is a major cause of hospital acquired infection and is the leading cause of antibiotic-associated diarrhea. In the past decade, two epidemic ribotypes (RT027 and RT078) of C. difficile have emerged as major ribotypes in hospital outbreaks around the world despite not being observed at significant levels prior to the year 2000. These ribotypes are associated with increased morbidity and mortality and have been classified as hypervirulent. However, the mechanistic basis for why these strains began to emerge in the early 2000s is unclear. We have found that RT027 and RT078 strains have acquired the ability to grow on the disaccharide trehalose more efficiently than other ribotypes of C. difficile. Our preliminary data shows that the mechanistic bases for the improved growth in these two ribotypes are genetically and mechanistically distinct, suggesting convergent evolution of improved trehalose metabolism in these phylogenetically distinct ribotypes. In addition, we have found that disrupting the ability of a RT027 strain to utilize trehalose dramatically attenuates disease severity, suggesting that trehalose metabolism contributes to the hypervirulent nature of RT027 and RT078 strains. Trehalose, a disaccharide of glucose, became a widely used food supplement after being granted GRAS status approval by the FDA in 2000 and EFSA in Europe in 2001. Trehalose has a number of desirable properties as a sugar additive due to the alpha, alpha 1-1 linkage that is heat and acid stable, which renders it 45% less sweet than sucrose. Normally found in foods such as mushrooms and shellfish, trehalose is now added to numerous food and drink products ranging from ground beef to ice cream. The addition of trehalose to the worldwide food supply coincides with the first reports of RT027 and RT078 strains in the early 2000s, even though these ribotypes were present in hospitals as far back as 1985. We propose that addition of increased levels of trehalose to the food supply has selected for RT027 and RT078 strains due to their ability to more efficiently metabolize trehalose and has contributed to hospital epidemics. We will use two recently developed models in our laboratory, human fecal minibioreactor array model of C. difficile invasion and a humanized microbiota mouse model of C. difficile infection, to study the impact of trehalose and improved trehalose metabolism on the ability of RT027 and RT078 strains to cause C. difficile infection. We will also investigate the mechanistic bases for improved trehalose metabolism of RT027 and RT078 strains. Finally, we will assess what impact improved trehalose metabolism has on colonization dynamics, disease severity and carriage in animals of these hypervirulent C. difficile ribotypes. The following specific aims are proposed: Aim 1. Investigate the mechanism of how trehalose metabolism by C. difficile increases disease severity. Aim 2. Understand the mechanistic basis for improved trehalose metabolism in RT027 C. difficile. Aim 3. Understand the role of the acquired trehalose operon on RT078 fitness and animal carriage. We expect this work will establish a link between the recent addition of trehalose in the human diet and the emergence of epidemic C. difficile ribotypes. This will provide the first direct evidence of the alteration of the human diet directly impacting the pathogenesis of an enteric infection.