The Importance of the Microbiome in Critically Ill Patients: Role of Nutrition

Abstract

Critically ill patients have an alteration in the microbiome in which it becomes a disease-promoting pathobiome. It is characterized by lower bacterial diversity, loss of commensal phyla, like Firmicutes and Bacteroidetes, and a domination of pathogens belonging to the Proteobacteria phylum. Although these alterations are multicausal, many of the treatments administered to these patients, like antibiotics, play a significant role. Critically ill patients also have a hyperpermeable gut barrier and dysregulation of the inflammatory response that favor the development of the pathobiome, translocation of pathogens, and facilitate the emergence of sepsis. In order to restore the homeostasis of the microbiome, several nutritional strategies have been evaluated with the aim to improve the management of critically ill patients. Importantly, enteral nutrition has proven to be more efficient in promoting the homeostasis of the gut microbiome compared to parenteral nutrition. Several nutritional therapies, including prebiotics, probiotics, synbiotics, and fecal microbiota transplantation, are currently being used, showing variable results, possibly due to the unevenness of clinical trial conditions and the fact that the beneficial effects of probiotics are specific to particular species or even strains. Thus, it is of great importance to better understand the mechanisms by which nutrition and supplement therapies can heal the microbiome in critically ill patients in order to finally implement them in clinical practice with optimal safety and efficacy.

A key role of gut microbiota-vagus nerve axis and gut microbiota-spleen axis in sleep deprivation-mediated aggravation of systemic inflammation after LPS administration

“…It is shown that increased abundance of proteobacteria community in the gut might contribute to low-fat/high-sugar diet-induced liver damage and high-fat dietinduced psychiatric disorders in mice [39,40]. Proteobacteria is the dominant phyla in septic patients [41,42]. To determine the causal link between post-septic SD-induced aggravation of systemic in ammation and gut microbiome, pseudo germ-free mice were constructed as recipients receiving fecal microbiota from septic mice with or without SD.…”

Effect of gut microbiota modulation on feeding tolerance of enterally-fed critically ill adult patients: a systematic review

“…These changes are due to alterations in gut muscle contractions, secretion, and absorption. Gut microbiota disturbances and epithelial barrier disintegration are also involved (3)(4)(5). In this situation, early-onset and the proper amount of nutrition support are of great importance (6).…”

“…Enteral nutrition (EN) is regarded as the favored root of nutrition support, because it protects the gut barrier, modulates immune responses, and leads to a faster return of gut function. However, many critical care patients cannot receive EN due to tolerance problems (4,6).…”

Temporal Fluctuations of Gut Microbiota and Bile Acid Metabolism in Critically Ill Children

“…The effects of broad-spectrum antimicrobials on the microbiota, and the subsequent recovery process, have been well documented [10][11][12]. However, critical illness can have profound effects on feeding and energy intake [13], and respiratory complications may lead to low oxygen saturation and subsequent hypoxia, inducing disruption of the gut microbiota [14]. Furthermore, changes in the structure of the microbiota may exacerbate the disease state or alter the course of recovery [3,12,15].…”