Gut microbiota plays an essential role in health and disease. It is constantly evolving and in permanent communication with its host. The gut microbiota is increasingly seen as an organ, and its failure, reflected by dysbiosis, is seen as an organ failure associated with poor outcomes. Critically ill patients may have an altered gut microbiota, namely dysbiosis, with a severe reduction in “health-promoting” commensal intestinal bacteria (such as Firmicutes or Bacteroidetes) and an increase in potentially pathogenic bacteria (e.g. Proteobacteria). Many factors that occur in critically ill patients favour dysbiosis, such as medications or changes in nutrition patterns. Dysbiosis leads to several important effects, including changes in gut integrity and in the production of metabolites such as short-chain fatty acids and trimethylamine N-oxide. There is increasing evidence that gut microbiota and its alteration interact with other organs, highlighting the concept of the gut–organ axis. Thus, dysbiosis will affect other organs and could have an impact on the progression of critical diseases. Current knowledge is only a small part of what remains to be discovered. The precise role and contribution of the gut microbiota and its interactions with various organs is an intense and challenging research area that offers exciting opportunities for disease prevention, management and therapy, particularly in critical care where multi-organ failure is often the focus. This narrative review provides an overview of the normal composition of the gut microbiota, its functions, the mechanisms leading to dysbiosis, its consequences in an intensive care setting, and highlights the concept of the gut–organ axis.

中文翻译：

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肠道菌群在危重病人中的核心作用和生物动力学作用

肠道微生物群在健康和疾病中起着至关重要的作用。它在不断发展，并与宿主保持永久联系。肠道微生物群越来越多地被视为一个器官，其功能障碍（表现为生态失调）被视为与不良结果相关的器官衰竭。重症患者的肠道菌群可能发生改变，即菌群失调，“促进健康”的肠道共生细菌（如厚壁菌门或拟杆菌门）严重减少，潜在致病菌（如变形杆菌门）增加。危重患者中发生的许多因素都支持生态失调，例如药物治疗或营养模式的改变。生态失调会导致几个重要影响，包括肠道完整性的变化和代谢物（如短链脂肪酸和三甲胺 N-氧化物）的产生。越来越多的证据表明肠道微生物群及其改变与其他器官相互作用，突出了肠道-器官轴的概念。因此，生态失调会影响其他器官，并可能对严重疾病的进展产生影响。目前的知识只是尚待发现的一小部分。肠道微生物群的确切作用和贡献及其与各种器官的相互作用是一个激烈且具有挑战性的研究领域，为疾病预防、管理和治疗提供了令人兴奋的机会，特别是在多器官衰竭经常成为焦点的重症监护中。这篇叙述性综述概述了肠道微生物群的正常组成、其功能、导致生态失调的机制、其在重症监护环境中的后果，