Recent Insights into the Evolving Role of the Gut Microbiome in Critical Care

Abstract

This review explores the evolving understanding of gut microbiota's role in critical illness, focusing on how acute illness and exposures in intensive care unit (ICU) environment negatively impact the gut microbiota and the implications of these changes on host responses in critically-ill patients. Focusing on recent findings from clinical and preclinical studies, we discuss the effects of inflammation, enteral nutrient deprivation, and antibiotics on gut microbial dynamics. This review aims to enhance comprehension of microbial dynamics in the ICU and their implications for clinical outcomes and therapeutic strategies.

Keywords: Bacterial extracellular vesicles; Critical care; Gut hyperpermeability; Microbiome; Nutrition.

Fig. 1.

The intensive care unit (ICU) gut microbiota features a reduction in biodiversity and loss of Firmicutes (ie, Bacillota by current nomenclature). Panels depict unpublished work from landmark study by McDonald et al. that used 16S rRNA sequencing of fecal samples from 162 ICU patients and 199 healthy controls from the American Gut Project (AGP) to identify significant changes in the gut microbiota throughout ICU stay. Left panel demonstrates differences in diversity. Right panel demonstrates Principal-coordinate (PC) plot of distributions of Firmicutes representation (vast majority belonging to the Clostridiales order) among ICU patients (n = 135 samples) and healthy patients (n = 2640 samples) with sphere color denoting relative abundance within each sample. (Data used with permission from Dr McDonald and Dr Knight; see reference #15 for full article.)