Dietary and synbiotic strategy to limit gut microbiome dysbiosis and protect against Clostridioides difficile infection

摘要 艰难梭状芽胞杆菌感染(CDI)是发病率和死亡率的重要原因，且发病率呈上升趋势。 这表明迫切需要安全和新的方法来治疗和预防。新出现的证据 提示高脂肪/低纤维饮食可能促进CDI。高饱和脂肪饮食会导致 一种初级胆汁酸，可通过滋生艰难梭菌孢子而促进感染。缺乏纤维的饮食 使艰难梭菌在小鼠体内永久定植，这种影响至少部分与短链的丢失有关 脂肪酸(SCFA)。我们的初步小鼠研究表明，高脂肪/低纤维饮食导致 广谱抗生素挑战后的微生物群紊乱，盲肠初级胆汁水平升高 催生艰难梭菌孢子的酸显著降低了杀死艰难梭菌孢子的次级胆汁酸水平。 艰难梭菌，暴露于艰难梭菌会增加发病率和死亡率。这些结果表明，饮食 干预措施有望预防高危人群的CDI。目标1A将确定以下各项的影响 膳食脂肪和纤维水平在预防抗生素引起的肠道微生物群紊乱和CDI中的作用 用传统的小鼠喂食不同的食物。Aim 1B将直接评估肠道增加的作用 艰难梭菌通过化学抑制回肠致病的初级胆汁酸水平 心尖钠依赖胆盐转运体。肿瘤患者CDI发生率高，受风险驱动 这些因素包括频繁住院、抗生素使用和化疗药物的使用。AIM 2将测试 高纤维/低脂肪饮食干预预防艰难梭菌复发和维持 肿瘤患者肠道微生物群多样性的研究。单链脂肪酸的产生可能是一种机制 对CDI中纤维的保护作用。肠上皮细胞对单链脂肪酸丁酸盐的代谢作用 在建立肠道缺氧中起关键作用，这一点很重要，因为恢复到缺氧状态是一个关键 促进厌氧菌为主的复合肠道微生物群重建的过程 骚乱。从纤维中生产超临界脂肪酸仅限于复杂性较低的兼性厌氧菌-- 以微生物群为主，这在复发性CDI患者中很常见。在我们早期的工作中，我们有 已确定的丁酸酯生产商，包括共生梭菌和厌氧菌，它们专门生产 婴儿和紊乱的肠道，可以用一种简单的底物葡萄糖酸作为鞋底产生丁酸 碳的来源。因此，在目标3中，我们将检验如下假设：合生生物治疗与干扰 适应的丁酸生产者和葡萄糖酸将增加丁酸盐的产量，增加肠道 低氧和促进厌氧次级胆汁酸产生的活动，以防止CDI，使用 被干扰的/低复杂性微生物区系人性化的小鼠。

Summary Clostridioides difficile infection (CDI) is an important cause of morbidity and mortality and rates are on the rise, indicating that safe and new approaches are urgently needed for treatment and prevention. Emerging evidence suggests that a high-fat/low-fiber diet may promote CDI. Diets high in saturated fat lead to the production of primary bile acids that can promote infection by germinating C. difficile spores. Diets deficient in fiber perpetuate C. difficile colonization in mice, and this effect was linked at least in part with a loss of Short Chain Fatty Acids (SCFAs). Our preliminary murine studies show that a high-fat/low-fiber diet resulted in increased microbiome disturbance following broad spectrum antibiotic challenge, increased cecal levels of primary bile acids that germinate C. difficile spores, markedly decreased levels of secondary bile acids that can kill C. difficile, and increased morbidity and mortality upon C. difficile exposure. These results suggest that dietary intervention has promise for preventing CDI in individuals at high risk. Aim 1A will determine the effects of dietary levels of fat and fiber in preventing antibiotic induced gut microbiome disturbance and CDI, using conventional mice fed varied diets. Aim 1B will directly evaluate the role of increased intestinal levels of primary bile acids in the increased C. difficile pathogenicity by chemically inhibiting the ileal apical sodium-dependent bile salt transporter. Oncology patients have high incidence of CDI, driven by risk factors that include frequent hospitalization, antibiotic use, and use of chemotherapeutic drugs. Aim 2 will test a higher-fiber/lower-fat dietary intervention for prevention of C. difficile recurrence and maintenance of gut microbiome diversity in oncology patients. Production of SCFAs may be one mechanism contributing to the protective effects of fiber in CDI. Metabolism of the SCFA butyrate by intestinal epithelial cells plays a key role in the establishment of intestinal hypoxia, which is important because reversion to hypoxia is a key process in promoting the reestablishment of an anaerobe dominated complex gut microbiome following disturbance. SCFA production from fiber is limited in individuals with a low complexity facultative anaerobe- dominated microbiome, which is common in individuals with recurrent CDI. In our earlier work, we have identified butyrate-producers, including Clostridium symbiosum and Anaerostipes caccae that specialize to infant and disturbed guts and that can produce butyrate using a simple substrate, gluconic acid, as a sole source of carbon. Thus, in Aim 3 we will test the hypothesis that synbiotic treatment with disturbance adapted butyrate-producers and gluconic acid will increase butyrate production, increase intestinal hypoxia and facilitate the activity of anaerobic secondary bile acid producers that prevent CDI, using mice humanized with a disturbed/ low-complexity microbiota.