Significant changes in the fecal bacteriobiota richness and diversity in patients with relapsing-remitting multiple sclerosis compared to healthy individuals.

PURPOSE: The aim of this study was to analyze gut microbiota composition and the distribution of Escherichia coli virulence-associated genes in patients with relapsing-remitting multiple sclerosis (RRMS) compared with healthy controls. The gut microbiota has been increasingly implicated in the pathogenesis of multiple sclerosis (MS) through its role in immune regulation and the gut-brain axis. METHODS: We analyzed gut microbiota composition in relapsing-remitting multiple sclerosis (RRMS) patients (n = 68) and healthy controls (n = 58) using 16S rRNA next-generation sequencing. RESULTS: Although phylum-level composition was similar between groups, with Firmicutes and Bacteroidota predominating, RRMS patients showed significantly reduced microbial richness and diversity, reflected by lower observed ASVs and Shannon index values. Beta diversity analysis (Bray-Curtis) revealed significant differences between groups (PERMANOVA, p = 0.001). Differential abundance analysis identified several genera enriched in RRMS patients, including Lactobacillus, UBA1819, Escherichia-Shigella, [Eubacterium]_fissicatena_group, Eisenbergiella, Streptococcus and [Clostridium]_innocuum_group (padj < 0.05). Analysis of typical E. coli virulence-associated genes showed distinct distribution patterns between groups, with cnf1 and hlyA more common in controls, whereas fimG/H and papC were more frequent in RRMS patients. CONCLUSION: These findings indicate that RRMS is associated with selective alterations in gut microbiota composition and shifts in the distribution of E. coli virulence-related genes rather than broad taxonomic changes.