Altering Routine Intensive Care Unit Practices to Support Commensalism.

The gastrointestinal (GI) tract consists of trillions of organisms that support multiple functions in the body, from immunity, digestion, and absorption to drug metabolism. These microbes form an overall collection of microorganisms that form the body's microbiome. In critical illness, many of these functions are aberrant, and the microbiome is altered, leading to untoward effects. Some of the most common medications received by patients include antibiotics and proton pump inhibitors, which affect particular changes in the microbiome. In addition, patients receiving prolonged enteral and parenteral nutrition experience changes in the microbiological composition and diversity of their GI tracts. Research is ongoing to characterize the crosstalk between the microbiome and immune function as targets for drug and nutrition therapy.