Diet driven evolution of epidemic ribotypes of Clostridium difficile

病原体的出现会导致发病率和死亡率的增加，这是一个主要的公共卫生问题 担忧。艰难梭菌是医院获得性感染的主要原因，也是 抗生素相关性腹泻。在过去的十年中，艰难梭菌的两个流行核糖型(RT027和RT078) 在世界各地的医院中作为主要的核糖体暴发出现，尽管没有在 2000年以前的显著水平。这些核型与发病率和死亡率的增加有关。 并已被归类为超强毒力。然而，这些菌株开始产生的机制基础 出现在21世纪初的情况尚不清楚。 我们发现RT027和RT078菌株已经获得了在双糖上生长的能力 海藻糖比艰难梭菌的其他核糖型更有效。我们的初步数据显示， 这两种核糖体类型生长改善的基础在基因和机制上是不同的，这表明 在这些系统发育不同的核型中，改进的海藻糖代谢的趋同进化。此外, 我们已经发现，干扰RT027菌株利用海藻糖的能力可以显著减轻疾病 严重程度，表明海藻糖代谢有助于RT027和RT078的超强毒力 菌株。海藻糖，一种葡萄糖的二糖，在被批准后成为一种广泛使用的食品补充剂 2000年FDA批准了GRAS的地位，2001年EFSA在欧洲批准了GRAS。海藻糖具有许多可取的 由于α，α1-1键是耐热和耐酸的，所以它具有作为糖添加剂的性质 比蔗糖低45%的甜度。海藻糖通常存在于蘑菇和贝类等食物中，现在 添加到从碎牛肉到冰淇淋的众多食品和饮料产品中。 在全球粮食供应中添加海藻糖与RT027和RT027的第一份报告不谋而合 21世纪初的RT078菌株，尽管这些核型早在1985年就存在于医院。 我们建议在RT027和RT027中选择在食物供应中增加海藻糖水平 RT078菌株由于能够更有效地代谢海藻糖而被送往医院 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 艰难梭菌入侵模型和人源化微生物群感染艰难梭菌小鼠模型的研究 海藻糖和改进的海藻糖代谢对RT027和RT078菌株产生C. 艰难梭菌感染。我们还将研究RT027改善海藻糖代谢的机制基础 和RT078菌株。最后，我们将评估改进的海藻糖代谢对定植的影响。 这些超强毒力艰难梭菌核型的动力学、疾病严重性和动物携带情况。以下是 提出了具体的研究目标：目的1.研究C。 难治性肺炎增加了疾病的严重性。目标2.了解改良海藻糖的机理基础 艰难梭菌在RT027中的代谢目的3.了解获得性海藻糖操纵子的作用 RT078健身和动物马车。我们希望这项工作将在最近增加的 人类饮食中的海藻糖和流行的艰难梭菌核型的出现。这将提供第一个 人类饮食变化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.