Modulators of the Microbiota on the ICU
The healthy intestinal microbiota is affected primarily by the host and the diet. In critically ill patients, these two factors both play an important role. However, in the critically ill it is also important to note that pathogens are able to outcompete other members of the intestinal microbiota more easily than in healthy humans, also changing the microbial composition. These pathogens benefit from a changed environment in critically ill patients, which are (though not per se all at the same time) decreased transit time, lack of 'normal' nutrition, oxygen levels and antibiotic usage.[1] Most of these opportunistic pathogens, except for Clostridium difficile infections, are Gram-negative aerobic species belonging to the proteobacteria, which thrive under the changed environment in critically ill patients. The universal use of antibiotics is probably the main cause of the severe bacterial dysbiosis seen in patients admitted to the ICU.[32–36] In addition, because of no or limited nutritional intake by patients on the ICU, nutrition for the microbiota in the intestine also decreases, affecting the microbiota composition. For example, in the large intestine, the microbiota ferments non-digested dietary fibers and dietary and host-derived proteins. The fermentation of fibers is necessary for the production of butyrate by the microbiota, which epithelial cells use as an energy source. The study of the clinical relevance of these effects in critically ill patients is, however, still in its infancy.
Crit Care. 2018;22(78) © 2018 BioMed Central, Ltd.
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