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

总结 艰难梭菌感染（CDI）是发病率和死亡率的重要原因，并且发病率呈上升趋势， 这表明迫切需要安全和新的治疗和预防方法。新出现的证据 表明高脂肪/低纤维饮食可能会促进CDI。高饱和脂肪的饮食会导致 初级胆汁酸可以通过萌发C.艰难孢子膳食纤维缺乏 使C.艰难梭菌在小鼠中的定植，并且这种效应至少部分与短链的损失有关。 脂肪酸（SCFAs）。我们的初步小鼠研究表明，高脂肪/低纤维饮食导致增加 广谱抗生素激发后的微生物组紊乱，盲肠原发性胆汁水平升高 使C.艰难梭菌孢子，可杀死C. 艰难梭菌，并增加发病率和死亡率后，C。艰难的暴露。这些结果表明，饮食 干预有望预防高危个体CDI。目标1A将决定 饮食中的脂肪和纤维水平预防抗生素诱导的肠道微生物组紊乱和CDI， 用的是喂养不同饮食的普通小鼠。目的1B将直接评估增加肠道的作用， 增加的C.艰难梭菌的致病性通过化学抑制回肠 顶端钠依赖性胆盐转运蛋白。肿瘤患者CDI的发生率较高，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。目标2将测试 高纤维/低脂肪饮食干预预防C.难治性复发和维持 肿瘤患者的肠道微生物组多样性。SCFAs的产生可能是一种机制， CDI中纤维的保护作用。肠上皮细胞对SCFA丁酸盐的代谢起着重要作用。 在建立肠道缺氧中起关键作用，这很重要，因为恢复缺氧是一个关键 促进厌氧微生物占主导地位的复杂肠道微生物组的重建的方法， 扰动从纤维中产生SCFA在具有低复杂性兼性厌氧菌的个体中是有限的- 占主导地位的微生物组，这在复发性CDI患者中很常见。在我们早期的工作中，我们有 已确定的丁酸盐生产商，包括共生梭菌和Anaerostipes caccae，专门用于 婴儿和受干扰的肠道，可以使用简单的底物葡萄糖酸作为唯一的底物来产生丁酸 碳源。因此，在目标3中，我们将检验合生素治疗与干扰 适应丁酸生产者和葡萄糖酸将增加丁酸生产，增加肠道 缺氧和促进厌氧二级胆汁酸生产者的活动，防止CDI，使用 用紊乱/低复杂性微生物群人源化的小鼠。

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.