BACKGROUND The digestive tract represents an interface between the external environment and the body where the interaction of a complex polymicrobial ecology has an important influence on health and disease. The physiological mechanisms that are altered during hospitalization and in the intensive care unit (ICU) contribute to the pathobiota's growth. Intestinal dysbiosis occurs within hours of being admitted to ICU. This may be due to different factors, such as alterations of normal intestinal transit, administration of various medications, or alterations in the intestinal wall, which causes a cascade of events that will lead to the increase of nitrates and decrease of oxygen concentration, and the liberation of free radicals. OBJECTIVE This work aims to report the latest updates on the microbiota's contribution to developing sepsis in patients in the ICU department. In this short review, the latest scientific findings on the mechanisms of intestinal immune defenses performed both locally and systemically have been reviewed. Additionally, we considered it necessary to review the literature on the basis of the many studies carried out on the microbiota in the critically ill as a prevention to the spread of the infection in these patients. MATERIALS AND METHODS This review has been written to answer four main questions: 1- What are the main intestinal flora's defense mechanisms that help us to prevent the risk of developing systemic diseases? 2- What are the main Systemic Abnormalities of Dysbiosis? 3- What are the Modern Strategies Used in ICU to Prevent the Infection Spreading? 4- What is the Relationship between COVID-19 and Microbiota? We reviewed 72 articles using the combination of following keywords: "microbiota" and "microbiota" and "intensive care", "intensive care" and "gut", "critical illness", "microbiota" and "critical care", "microbiota" and "sepsis", "microbiota" and "infection", and "gastrointestinal immunity" in: Cochrane Controlled Trials Register, Cochrane Library, Medline and Pubmed, Google Scholar, Ovid/Wiley. Moreover, we also consulted the site ClinicalTrials.com to find out studies that have been recently conducted or are currently ongoing. RESULTS The critical illness can alter intestinal bacterial flora leading to homeostasis disequilibrium. Despite numerous mechanisms, such as epithelial cells with calciform cells that together build a mechanical barrier for pathogenic bacteria, the presence of mucous associated lymphoid tissue (MALT) which stimulates an immune response through the production of interferon-gamma (IFN-y) and THN-a or or from the production of anti-inflammatory cytokines produced by lymphocytes Thelper 2. But these defenses can be altered following hospitalization in ICU and lead to serious complications, such as acute respiratory distress syndrome (ARDS), health care associated pneumonia (HAP) and ventilator associated pneumonia (VAP), systemic infection and multiple organ failure (MOF), but also to the development of coronary artery disease (CAD). In addition, the microbiota has a significant impact on the development of intestinal complications and the severity of the SARS-COVID-19 patients. CONCLUSION The microbiota is recognized as one of the important factors that can worsen the clinical conditions of patients who are already very frail in the intensive care unit. At the same time, the microbiota also plays a crucial role in the prevention of ICU-associated complications. By using the resources that are available, such as probiotics, synbiotics or fecal microbiota transplantation (FMT), we can preserve the integrity of the microbiota and the GUT, which will later help maintain homeostasis in ICU patients.

中文翻译：

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重症监护中的微生物组：一个非常规和未知的盟友。

背景技术消化道是外部环境与身体之间的界面，其中复杂的多微生物生态系统的相互作用对健康和疾病具有重要影响。在住院期间和重症监护病房 (ICU) 中改变的生理机制有助于病原菌群的生长。肠道菌群失调会在入住 ICU 后数小时内发生。这可能是由于不同的因素造成的，例如正常肠道运输的改变、各种药物的给药或肠壁的改变，导致一系列事件导致硝酸盐增加和氧气浓度降低，以及释放自由基。目标 这项工作旨在报告微生物群的最新更新。s 对 ICU 部门患者发生脓毒症的贡献。在这篇简短的综述中，对局部和全身性肠道免疫防御机制的最新科学发现进行了综述。此外，我们认为有必要根据对危重患者微生物群进行的许多研究来回顾文献，以预防这些患者的感染传播。材料和方法 本综述旨在回答四个主要问题： 1- 主要肠道菌群是什么？帮助我们预防发生全身性疾病风险的防御机制？2- 生态失调的主要系统性异常是什么？3- ICU 中用于防止感染传播的现代策略是什么？4- COVID-19 和微生物群之间的关系是什么？我们使用以下关键词的组合审查了 72 篇文章：“微生物群”和“微生物群”和“重症监护”、“重症监护”和“肠道”、“危重病”、“微生物群”和“重症监护”、“微生物群”和“败血症”、“微生物群”和“感染”以及“胃肠道免疫”，收录于：Cochrane 对照试验注册库、Cochrane 图书馆、Medline 和 Pubmed、Google Scholar、Ovid/Wiley。而且，我们还咨询了网站 ClinicalTrials.com 以了解最近进行或正在进行的研究。结果危重病可改变肠道菌群，导致体内平衡不平衡。尽管存在许多机制，例如上皮细胞与钙状细胞共同为病原菌建立机械屏障，但粘液相关淋巴组织 (MALT) 的存在通过产生干扰素-γ (IFN-y) 和 THN 来刺激免疫反应-a 或由淋巴细胞 Thelper 2 产生的抗炎细胞因子产生。但这些防御可能在 ICU 住院后发生改变，并导致严重的并发症，如急性呼吸窘迫综合征 (ARDS)、医疗相关性肺炎 (HAP) ) 和呼吸机相关性肺炎 (VAP)，全身感染和多器官衰竭（MOF），也会发展为冠状动脉疾病（CAD）。此外，微生物群对肠道并发症的发展和 SARS-COVID-19 患者的严重程度有显着影响。结论 微生物群被认为是可能使重症监护病房中已经非常虚弱的患者的临床状况恶化的重要因素之一。同时，微生物群在预防ICU相关并发症中也起着至关重要的作用。通过使用可用的资源，例如益生菌、合生元或粪便微生物群移植 (FMT)，我们可以保持微生物群和 GUT 的完整性，这将有助于维持 ICU 患者的体内平衡。还会导致冠状动脉疾病 (CAD) 的发展。此外，微生物群对肠道并发症的发展和 SARS-COVID-19 患者的严重程度有显着影响。结论 微生物群被认为是可能使重症监护病房中已经非常虚弱的患者的临床状况恶化的重要因素之一。同时，微生物群在预防ICU相关并发症中也起着至关重要的作用。通过使用可用的资源，例如益生菌、合生元或粪便微生物群移植 (FMT)，我们可以保持微生物群和 GUT 的完整性，这将有助于维持 ICU 患者的体内平衡。还会导致冠状动脉疾病 (CAD) 的发展。此外，微生物群对肠道并发症的发展和 SARS-COVID-19 患者的严重程度有显着影响。结论 微生物群被认为是可能使重症监护病房中已经非常虚弱的患者的临床状况恶化的重要因素之一。同时，微生物群在预防ICU相关并发症中也起着至关重要的作用。通过使用可用的资源，例如益生菌、合生元或粪便微生物群移植 (FMT)，我们可以保持微生物群和 GUT 的完整性，这将有助于维持 ICU 患者的体内平衡。微生物群对肠道并发症的发展和 SARS-COVID-19 患者的严重程度有重大影响。结论 微生物群被认为是可能使重症监护病房中已经非常虚弱的患者的临床状况恶化的重要因素之一。同时，微生物群在预防ICU相关并发症中也起着至关重要的作用。通过使用可用的资源，例如益生菌、合生元或粪便微生物群移植 (FMT)，我们可以保持微生物群和 GUT 的完整性，这将有助于维持 ICU 患者的体内平衡。微生物群对肠道并发症的发展和 SARS-COVID-19 患者的严重程度有重大影响。结论 微生物群被认为是可能使重症监护病房中已经非常虚弱的患者的临床状况恶化的重要因素之一。同时，微生物群在预防ICU相关并发症中也起着至关重要的作用。通过使用可用的资源，例如益生菌、合生元或粪便微生物群移植 (FMT)，我们可以保持微生物群和 GUT 的完整性，这将有助于维持 ICU 患者的体内平衡。结论 微生物群被认为是可能使重症监护病房中已经非常虚弱的患者的临床状况恶化的重要因素之一。同时，微生物群在预防ICU相关并发症中也起着至关重要的作用。通过使用可用的资源，例如益生菌、合生元或粪便微生物群移植 (FMT)，我们可以保持微生物群和 GUT 的完整性，这将有助于维持 ICU 患者的体内平衡。结论 微生物群被认为是可能使重症监护病房中已经非常虚弱的患者的临床状况恶化的重要因素之一。同时，微生物群在预防ICU相关并发症中也起着至关重要的作用。通过使用可用的资源，例如益生菌、合生元或粪便微生物群移植 (FMT)，我们可以保持微生物群和 GUT 的完整性，这将有助于维持 ICU 患者的体内平衡。