BACKGROUND
Polyethylene glycol (PEG)-based bowel preparation before colonoscopy can disrupt gut microbiota, particularly in patients with ulcerative colitis (UC), who already exhibit baseline dysbiosis and impaired microbial resilience. This study evaluated microbiota recovery after bowel preparation and the effects of probiotic supplementation.
MATERIAL AND METHODS
In this single-center, open-label trial (ChiCTR2200064456), 79 participants (40 healthy controls and 39 patients with UC) undergoing colonoscopy were randomized to receive probiotics or no probiotics for 28 days after colonoscopy. Fecal samples collected at baseline and on days 2, 14, and 28 were analyzed using 16S rRNA gene sequencing to assess microbial diversity, composition, and predicted functional pathways.
RESULTS
Bowel preparation significantly reduced a diversity and altered β diversity in healthy controls, with gradual recovery by day 28. patients with UC exhibited lower baseline diversity and delayed microbiota recovery. Probiotic supplementation modestly improved microbial recovery in healthy individuals and more substantially improved Shannon diversity and evenness in patients with UC. Probiotics were associated with enrichment of beneficial short-chain fatty acid–producing taxa, including Faecalibacterium, Blautia, and Lachnospiraceae, together with reductions in Proteobacteria and Fusobacteria. Predicted functional pathways related to energy metabolism and nucleotide biosynthesis were transiently suppressed after bowel preparation and showed partial recovery over time.
CONCLUSIONS
PEG-based bowel preparation induces reversible gut microbiota disruption, with slower recovery in patients with UC. Probiotic supplementation after colonoscopy was associated with improved microbial diversity and enrichment of beneficial taxa, particularly in patients with UC.

Keywords: Digestive System Diseases; Probiotics