Gut Microbiota Profiling of Lebanese Patients with Ulcerative Colitis and Healthy Controls: A Pilot Study

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon, associated with gut microbiota dysbiosis. While global studies have explored this link, region-specific microbial profiles remain underreported. This pilot study aimed to characterize and compare, for the first time, the gut microbiota of Lebanese UC patients and healthy controls using 16S rRNA gene sequencing (V3–V4 region). Fecal samples from 11 UC patients and 11 healthy individuals were analyzed. Alpha and beta diversity metrics were computed, and gut microbial composition was assessed across taxonomic levels. Statistical comparisons used Mann-Whitney and Fisher's exact tests. UC patients showed significantly reduced microbial diversity based on Faith's Phylogenetic Diversity and Shannon index (p < 0.05), though evenness was unaffected. Beta diversity also revealed significant group-level dissimilarities (p < 0.05). At the phylum level, Bacteroidota was elevated in UC, while Bacillota and Actinomycetota were reduced. Genera such as Ruminococcus, Fusicatenibacter, Mediterraneibacter, Eubacterium, and Coprococcus were depleted in UC. Faecalibacterium, commonly reduced in UC, showed no significant difference. This first analysis of gut microbiota in Lebanese UC patients reveals a distinct microbial signature that partially diverges from global trends, supporting the need for region-specific microbiome studies and personalized microbiota-targeted therapies. Overall design: Cross-sectional, observational, case-control pilot study using 16S rRNA gene sequencing.