P1352 Segmental Mucosal Microbiome Variations Across Different Inflammation Extents in Ulcerative Colitis
Authors: Shin J , Song J H , Cha B , Hong J T , Kwon K S , kim J S 
Published: January 2025

Abstract

Background
Ulcerative colitis (UC) is a chronic inflammatory condition characterized by a relapsing-remitting course and represents a major subtype of inflammatory bowel disease (IBD). The gut microbiome plays a pivotal role in the pathogenesis and progression of UC. However, the potential differences in the mucosal microbiome composition across colonic segments, depending on the extent of inflammation in UC, remain poorly explored.

Methods
we investigated the differences in the mucosal microbiome according to colonic segments in patients with proctitis (R), Lt side colitis (L), pancolitis (P) and remission (RE). A total of 36 UC patients who underwent endoscopic evaluation between March 2023 and July 2024 were finally enrolled. The patients were allocated by disease extent to R (n=18,50.0%), L (n=5, 13.9%), P (n=3, 8.3%) and RE (n=10, 27.8%) groups. The mucosal microbiomes of ascending colon (AC), descending colon (DC), and rectum (RT) were evaluated. Total genomic DNA was extracted from the samples, and the character of the microbiome was determined by sequencing the V3-V4 region of the 16s rRNA gene (Miseq).

Results
The mucosal microbiome of the RE group exhibited similar alpha diversity across all colonic segments. In contrast, the R and L groups demonstrated increased species richness and evenness in the rectum and descending colon compared to the RE group. However, P group showed consistently low species richness and diversity across all segments compared to the RE group, and with no significant segmental differences within the group. Taxonomic composition analysis at the genus level revealed that segments with active inflammation were enriched with Clostridium innocuum, Campylobacteria, Fusobacteriota, and Alistipes, while Serratia, Rhizorhapis, and Sediminibacterium were depleted compared to the RE group. In beta diversity, the microbiome composition was not different depending on the segment in the RE and P group. In the R and L group, the microbiome composition of the rectum and descending colon were similar but separate from the ascending colon.

Conclusion
In summary, the mucosal microbiome in inflamed segments differs from that in segments with remission. In cases of pancolitis, the mucosal microbiome exhibited no segmental differences but demonstrated a distinct overall pattern compared to other groups. Evaluating the segmental mucosal microbiome may offer valuable clinical insights into the progression of UC and aid in predicting the extent of inflammation.

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