Bowel Preparation-Induced Microbial Dysbiosis and Its Restoration by Probiotics in Ulcerative Colitis

Bowel preparation is essential for colonoscopy but significantly disturbs gut microbiota. Its impact on individuals with ulcerative colitis (UC), and the potential for probiotics to promote microbial recovery, remain underexplored. We collected 316 fecal samples from healthy individuals and UC patients at four time points: baseline, Day 2, Day 14, and Day 28 following bowel preparation with polyethylene glycol electrolyte solution (Registration Date: 2022-10-09; Registration Number: ChiCTR2200064456). 16S rRNA sequencing was used to assess microbial composition and diversity. A subset of participants received oral probiotic supplementation for 28 days post-colonoscopy to evaluate its impact on microbiota restoration. Bowel preparation significantly reduced gut microbiota diversity and altered microbial composition in both healthy and UC groups. In healthy individuals, these disruptions largely resolved by Day 14. In contrast, UC patients exhibited more pronounced and prolonged microbial dysbiosis. Notable taxonomic shifts included decreases in Blautia, Faecalibacterium, and Lachnospira, and increases in Escherichia-Shigella and Fusobacterium. Functional pathway analysis revealed transient downregulation of key metabolic pathways, including the pentose phosphate and purine biosynthesis pathways. Probiotic supplementation notably improved microbial diversity and increased beneficial butyrate-producing bacteria, particularly in UC patients. Metabolic function recovery was also enhanced by probiotics. Bowel preparation induces transient gut dysbiosis, with more severe and persistent effects in UC patients. Probiotic supplementation facilitates microbial and functional recovery, supporting its use as a post-preparation therapeutic strategy, especially in vulnerable populations such as UC patients.