Prebiotic Fiber to Prevent Pathogen Colonization in the ICU

This study will test prebiotic fiber in 20 adults who are receiving broad-spectrum antibiotics in the medical or surgical ICU by open-label randomization of patients to approximately 20 g prebiotic fiber/day including 45% short-chain fructooligosaccharides versus 0 g fiber/day by providing one of two feeds. Per 10 ounces of feed, both the high and low fiber feeds contain identical micronutrients and have 296 kilocalorie (kCal), 19 g protein, 8 g fat, and 39 g carbohydrates. The sole difference is that the fiber-containing feed has 4 g fiber including 45% short-chain fructooligosaccharides per 10 ounces whereas the other feed has 0 g fiber. Randomization will take place at the time the order for enteral feeding is placed. Rather than supplying the feed itself, the investigators will supply a randomized recommendation for a feed type (i.e., high vs low fiber) and the feed will be obtained from the hospital pharmacy in the usual manner. Determination of the feed rate and duration will be decided on the individual patient's needs by the treating ICU team. The primary outcome will be to determine whether high fiber feeds alter the gut microbiome in the face of antibiotics and critical illness, calculated by comparing within-individual microbiome differences from baseline to Day 3 in each intervention group.