The small intestine represents a complex and understudied gut niche with significant implications for human health. Indeed, many infectious and non‐infectious diseases center within the small intestine and present similar clinical manifestations to large intestinal disease, complicating non‐invasive diagnosis and treatment. One major neglected aspect of small intestinal diseases is the feedback relationship with the resident collection of commensal organisms, the gut microbiota. Studies focused on microbiota–host interactions in the small intestine in the context of infectious and non‐infectious diseases are required to identify potential therapeutic targets dissimilar from those used for large bowel diseases. While sparsely populated, the small intestine represents a stringent commensal bacterial microenvironment the host relies upon for nutrient acquisition and protection against invading pathogens (colonization resistance). Indeed, recent evidence suggests that disruptions to host–microbiota interactions in the small intestine impact enteric bacterial pathogenesis and susceptibility to non‐infectious enteric diseases. In this review, we focus on the microbiota's impact on small intestine function and the pathogenesis of infectious and non‐infectious diseases of the gastrointestinal (GI) tract. We also discuss gaps in knowledge on the role of commensal microorganisms in proximal GI tract function during health and disease.

中文翻译：

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结肠的漫长旅程：小肠微生物群在肠道疾病中的作用

小肠是一个复杂且未被充分研究的肠道生态位，对人类健康具有重大影响。事实上，许多感染性和非感染性疾病集中在小肠内，并呈现与大肠疾病相似的临床表现，使无创诊断和治疗变得复杂。小肠疾病的一个主要被忽视的方面是与共生生物（肠道微生物群）的常驻集合的反馈关系。需要针对传染性和非传染性疾病背景下小肠微生物群与宿主相互作用的研究，以确定与大肠疾病不同的潜在治疗靶点。虽然人口稀少，但小肠代表了宿主赖以获取营养和防止病原体入侵（定殖抗性）的严格共生细菌微环境。事实上，最近的证据表明，小肠中宿主与微生物群相互作用的破坏会影响肠道细菌的发病机制和对非传染性肠道疾病的易感性。在这篇综述中，我们重点关注微生物群对小肠功能的影响以及胃肠道（GI）感染性和非感染性疾病的发病机制。我们还讨论了关于共生微生物在健康和疾病期间近端胃肠道功能中的作用的知识差距。