Study Links Oral Bacteria to Multiple Sclerosis Severity

Growing evidence suggests that periodontitis, a severe gum disease driven by chronic inflammation, may contribute to disorders of the central nervous system. A study published in Scientific Reports  examines this connection in multiple sclerosis (MS), a chronic autoimmune disease that attacks the protective myelin sheath surrounding nerve cells. The research team focused on whether specific oral bacteria, particularly Fusobacterium nucleatum, are associated with the severity of MS symptoms.

The investigators from Hiroshima University analyzed tongue coating samples from patients with MS, neuromyelitis optica spectrum disorder (NMOSD), and myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD). They classified bacterial abundance as “high” or “low” depending on whether levels fell within the top or bottom quartiles, then compared these data with clinical measures. Their goal was to determine whether oral microbiota patterns, long known to affect systemic inflammation, might have a distinct influence on MS outcomes.

Results revealed a significant association between high relative abundance of F. nucleatum and increased disability among MS patients, as measured by the Expanded Disability Status Scale (EDSS). No similar pattern emerged in NMOSD or MOGAD patients. After accounting for age, disease duration, number of attacks, and MS subtype, individuals with elevated F. nucleatum levels had approximately tenfold greater odds of severe disability. About 61.5% of MS patients with high F. nucleatum levels showed moderate-to-severe disability (EDSS ≥ 4), compared with only 18.6% of those in the milder group. The effect appeared stronger when F. nucleatum was detected alongside other periodontal bacteria.

According to co-author Masahiro Nakamori, “While the gut microbiome has been extensively investigated in multiple sclerosis, the potential involvement of the oral microbiome has remained largely unexplored. Because the oral cavity is a major source of chronic inflammation and represents a potentially modifiable factor, clarifying its relationship with multiple sclerosis severity is important for understanding disease mechanisms and developing new preventive strategies.” 

The research team suggests that F. nucleatum may act as a “bridge bacterium,” linking oral infection to neurological inflammation. They plan further investigations to uncover the mechanisms driving this connection and to explore whether dental treatments or improved oral hygiene can affect MS progression.