Study finds differences in mouth bacteria among people with MS

A new study has found that people living with multiple sclerosis (MS) have distinct differences in the bacteria found in their mouths compared with people without the condition. The human microbiome is mostly located in the gut and many studies show the gut microbiome is dysregulated in MS. The mouth hosts the second most diverse microbiome in the body and changes in oral bacteria have been linked with other neurodegenerative diseases such as Alzheimer’s disease, but there has been far less research into how the oral microbiome is affected in MS.

Researchers at the University of Iowa analysed saliva samples from 50 people with relapsing remitting MS and 50 healthy controls. People with MS had lower levels of bacteria typically linked with good oral health, including Streptococcus and Actinomyces. They also had higher levels of bacteria associated with dental and gum disease, such as Fusobacterium nucleatum, Porphyromonas gingivalis, and Prevotella species.

The team also examined bacterial metabolites, the small molecules produced by bacteria, and found several differences between groups. Levels of hypotaurine, a molecule important for nerve cell development and maintenance of the myelin sheath, were notably lower in the MS group. Computer modelling suggested that normal networks between specific bacteria and metabolites seen in healthy mouths were disrupted in MS, pointing to a wider imbalance in the oral microbiome.

These findings add to growing evidence that microbiomes beyond the gut may be relevant in MS and could help inform future diagnostic markers or treatments. The study involved a relatively small number of participants and did not include dental health data, so larger studies are needed to confirm the results and to determine whether oral microbiome changes contribute to MS, result from the condition, or both.