A case-control study of the oral microbiome among Australian female adults with relapsing-remitting multiple...

There is growing evidence investigating the role of the gut microbiome in the onset and progression of multiple sclerosis (MS). However, the role of the oral microbiome in MS is poorly understood, despite its importance in immune regulation and systemic health.

A cross-sectional, case-control, pilot study comparing the oral microbiome among adults with relapsing-remitting MS to matched controls based on age, sex and body mass index (BMI), was conducted. Participants provided fasting oral swabs where DNA was extracted and shotgun metagenomic sequencing performed. Comparative analyses between cases and controls explored alpha-and beta-diversities including differential abundance testing.

Across 24 oral microbiome samples, 355 species from 12 phylum were detected. Alpha diversity was lower in MS at the species level, however, did not reach statistical significance for either richness or Shannon diversity. Beta diversity demonstrated a significant difference using Bray-Curtis dissimilarity with group status accounting for ∼6.7% of the total variation in microbial community structure. Differential abundance testing highlighted Veillonella parvula as the most enriched species among cases (coef=2.56, stderr=0.74, FDR=0.17), while Porphyromonas pasteri (coef=-3.57, stderr=1.02, FDR=0.17) and s__GGB4936_SGB6889 (coef=-4.29, stderr=1.30, FDR=0.17) were predominant among controls.

The oral microbiome of Australian females with RRMS differs in a subtle but detectable manner from those without MS, characterised by a non-significant trend towards reduced microbial diversity and distinct compositional clustering based on Bray-Curtis dissimilarity. Findings support the emerging concept of an oral-immune axis in MS, underscoring the need for longitudinal and functional studies to explore causality.