A higher oral abundance of the periodontal bacterium Fusobacterium nucleatum is associated with greater disability in patients with multiple sclerosis (MS), according to a cross-sectional study published in Scientific Reports.
The study, conducted at Hiroshima University Hospital in Japan, explored whether specific periodontal pathogens are linked to disease severity in central inflammatory demyelinating diseases. Researchers analyzed tongue coating samples from 98 patients, including 56 with MS, 31 with neuromyelitis optica spectrum disorder (NMOSD), and 11 with myelin oligodendrocyte glycoprotein antibody–associated disease (MOGAD). Quantitative polymerase chain reaction was used to measure the relative abundance of four periodontal bacteria.
Among patients with MS, those with a high relative abundance of F. nucleatum were more likely to have higher scores on the Expanded Disability Status Scale (EDSS), a standard measure of neurologic disability. Specifically, patients in the highest quartile for F. nucleatum abundance were significantly more likely to have an EDSS score of 4 or higher, a threshold associated with gait impairment. This association remained significant after adjustment for age, disease duration, and other clinical factors.
In contrast, no significant associations were found between disability severity and the other periodontal pathogens studied – Porphyromonas gingivalis, Prevotella intermedia, or Treponema denticola. The relationship between F. nucleatum and disability was also not observed in patients with NMOSD or MOGAD, suggesting a disease-specific association in MS.
The authors note that F. nucleatum is a common oral bacterium involved in periodontal disease and has previously been linked to systemic inflammation and vascular and neurologic conditions. Experimental and clinical evidence suggests that the bacterium may influence immune responses through pro-inflammatory pathways, although the current study was not designed to assess mechanisms.
Importantly, the researchers did not find differences in oral hygiene habits, such as tooth-brushing frequency or use of dental products, between patients with higher and lower disability scores. This suggests that bacterial abundance may not simply reflect differences in self-reported oral care.
The authors emphasize that the study’s cross-sectional design prevents conclusions about causality. They also acknowledge limitations, including the lack of formal periodontal examinations and the relatively small sample size. Further studies will be needed to determine whether oral microbiota contribute to MS progression or reflect underlying disease severity.
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