Oral bacteria tied to more severe multiple sclerosis symptoms
Study shows more F. nucleatum present in patients with higher disability scores
- Higher levels of the oral bacterium Fusobacterium nucleatum are linked to more severe MS symptoms.
- Patients with more F. nucleatum were more likely to show increased disability on the EDSS scale.
- The findings suggest oral health, and oral bacteria, may play a role in MS severity.
People with multiple sclerosis (MS) who have higher levels of Fusobacterium nucleatum in the mouth — bacteria that can contribute to periodontitis, a serious gum infection — may be more likely to experience more severe symptoms, according to a study from Japan.
This finding adds to recent preclinical evidence suggesting that periodontitis may be associated with a faster progression of MS, and that changes in the bacteria living deeper in the digestive tract — and their interactions with the immune system — may also influence aspects of the disease.
“F. nucleatum is present not only in the oral cavity but also in the gut,” researchers wrote in the study “The periodontal pathogen Fusobacterium nucleatum is associated with disease severity in multiple sclerosis,” published in Scientific Reports.
Periodontal disease and MS: earlier evidence points to a possible connection
Previous studies have shown that the gut microbiome — the community of bacteria and other microbes living in the intestines — becomes disrupted in MS. However, much less is known about the potential connections between bacteria living in other areas of the body and MS or similar conditions.
“With a global prevalence of 40–60%, periodontal disease is a common condition, and the presence of periodontal disease has been shown to increase the risk of developing systemic diseases such as atherosclerosis, diabetes, and rheumatoid arthritis,” the scientists wrote. “A meta-analysis further suggested that patients with chronic periodontitis have nearly twice the risk of developing MS. However, how periodontal disease influences clinical factors, relapse and progression in MS and whether the effects vary depending on the specific bacterial species involved remain unclear.”
To explore this further, the researchers collected tongue-surface samples from 98 patients — 56 with MS, 31 with neuromyelitis optica spectrum disorder, and 11 with myelin oligodendrocyte glycoprotein antibody-associated disease — with a mean age of 48.6. The samples were tested for four species of bacteria linked to periodontitis.
Brushing habits and use of dental products were similar across all three groups. People who scored four or more points on the Expanded Disability Status Scale (EDSS) — a scale ranging from zero (no disability) to 10 (death due to MS) — were more likely to be receiving dental treatment than those with lower scores (67.7% vs. 38.5%).
The researchers measured how much of each species was present by detecting its genetic material using a technique called quantitative polymerase chain reaction. A “high relative abundance” was defined as levels above the top 25% compared with all bacteria found in the mouth.
Only F. nucleatum shows a clear association with more severe MS symptoms
Out of all the bacteria analyzed, only F. nucleatum appeared to be linked to more severe MS symptoms. People with a “high relative abundance” of these bacteria were more likely to score four or more points on the EDSS than those with lower levels (61.5% vs. 18.6%), meaning they had more severe disability.
This association was not found with the other bacteria or in the two non-MS groups. Even after adjusting for other possible factors, the connection between higher levels of F. nucleatum and more severe disability remained significant. While this does not prove cause and effect, it suggests the bacterium may have an independent role in worsening symptoms of MS.
Patients who had high levels of F. nucleatum plus higher levels of other periodontal bacteria had a median EDSS score of 6.0, compared with 1.5 in other patients — a 4.5-point difference. They were also more likely to score four or above on the EDSS (37.5% vs. 10%). Separately, having a high relative abundance of F. nucleatum alone increased the odds of more severe disability by about 10-fold.
“These findings suggest a potential association between the relative abundance of Fusobacterium nucleatum in the oral cavity and disease severity in MS,” the researchers concluded, regardless of whether other periodontal bacteria were also present at high levels.
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