Effects of diets containing synbiotics on the gut microbiota of critically ill septic patients: a pilot randomized controlled trial

The effects of synbiotics on gut microbiota have not been thoroughly clarified in critically ill patients with sepsis. In this present study, we aimed to evaluate the effects of synbiotics in a commercial diet on the gut microbiota of mechanically ventilated septic patients. This double-blind, randomized controlled clinical trial was conducted on septic patients under mechanical ventilation in a university-affiliated hospital in southern Thailand from February 2019 to March 2021. The patients were randomly divided into 2 groups stratified by sepsis stages and given commercial enteral feeding with synbiotics or standard commercial feeding for 7 days. The primary outcome was fecal microbial diversity measured as alpha and beta diversity. The secondary outcomes included ventilator-associated pneumonia, nosocomial diarrhea, ventilator days, length of hospital stay, and mortality. Twenty-four patients, 12 on a synbiotic diet and 12 on a non-synbiotic diet, completed this study. On day 3 of feeding, no significant difference was observed in their alpha fecal microbial diversity. However, significantly greater beta diversity was observed in the non-synbiotics group compared with the synbiotic group (Bray Curtis distance, p = 0.001; Jaccard's distance, p = 0.001; unweighted UniFrac, p = 0.001; weighted UniFrac, p = 0.029). The secondary outcomes were not significantly different between the two groups. In critically ill septic patients, feeding with a commercial diet containing synbiotics did not significantly improve fecal microbial diversity. Due to the small sample size, further study is required.