The human gastrointestinal (GI) tract has been bestowed with the most difficult task of protecting the underlying biological compartments from the resident commensal flora and the potential pathogens in transit through the GI tract. It has a unique environment in which several defence tactics are at play while maintaining homeostasis and health. The GI tract shows myriad number of environmental extremes, which includes pH variations, anaerobic conditions, nutrient limitations, elevated osmolarity etc., which puts a check to colonization and growth of nonfriendly microbial strains. The GI tract acts as a highly selective barrier/platform for ingested food and is the primary playground for balance between the resident and uninvited organisms. This review focuses on antimicrobial defense mechanisms of different sections of human GI tract. In addition, the protective mechanisms used by microbes to combat the human GI defence systems are also discussed. The ability to survive this innate defence mechanism determines the capability of probiotic or pathogen strains to confer health benefits or induce clinical events respectively.

中文翻译：

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胃肠压力是抵抗微生物侵袭的先天防御

赋予人类胃肠道（GI）最艰巨的任务，就是保护其下面的生物区隔免受居民共生菌群和通过GI道传播的潜在病原体的侵害。它具有独特的环境，在此环境中，在维持体内平衡和健康的同时，采取了多种防御策略。胃肠道显示出无数的极端环境，包括pH值变化，厌氧条件，营养限制，渗透压升高等，这可以检查非友好微生物菌株的定殖和生长。胃肠道对摄入的食物起着高度选择性的屏障/平台的作用，并且是居民和非居民有机体之间保持平衡的主要场所。这篇综述着重于人类胃肠道不同部分的抗菌防御机制。此外，还讨论了微生物用来对抗人类胃肠道防御系统的保护机制。生存于先天防御机制的能力决定了益生菌或病原体菌株分别赋予健康益处或诱发临床事件的能力。