People With Multiple Sclerosis Have Distinct Oral Microbiome, Study Shows

Researchers from the University of Iowa Health Care have produced the most comprehensive analysis to date of the multiple sclerosis (MS) oral microbiome, according to research published recently in the journal npj Biofilms and Microbiomes.

“While the gut microbiome has long been linked to MS, the oral microbiome, our mouth’s rich microbial ecosystem, has received far less attention, even though it’s the second most diverse microbiome in the human body and has been linked with other neurological diseases, like Alzheimer’s disease and inflammatory diseases, like rheumatoid arthritis,” Ashutosh Mangalam, Ph.D., professor of pathology at the University of Iowa and senior author of the study, said in a news release.

The oral microbiome is home to more than 700 species of bacteria, and the average person hosts approximately 250 species at a time, according to the study. Each person’s oral microbiome is unique and changes over time, which is especially true for MS patients.

Mangalam and his team analyzed saliva from 50 people with relapsing-remitting MS (RRMS), which is the most common form of MS, and 50 without MS, using shotgun metagenomic sequencing and untargeted metabolomics.

The team found that people with MS had a disrupted oral microbiome when compared with people without MS. This manifested as an absence of “early colonizer bacteria” such as Streptococcus and Actinomyces, which are markers of a healthy oral bacterial community because they produce adhesive molecules that expedite the colonization of various oral tissues.

Researchers also noticed an increase in other disease-causing bacteria in MS patients, including Fusobacterium nucleatum and Porphyromonas gingivalis, which live in periodontal pockets and inflamed tissue and therefore might contribute to MS-related oral inflammation.

Additionally, when compared with healthy patients, MS patients also had lower levels of hypotaurine, a protective metabolite involved in antioxidant defense and nerve health.

The team also developed a program that allowed them to identify bacterial groups that coexist as communities, five of which are lost in MS patients.

“This multi-omics approach revealed how bacterial composition, function, and metabolite profiles are interconnected, highlighting specific bacterial taxa and metabolic signatures that may shape inflammation and immune dysregulation in MS,” Mangalam said. “These findings provide one of the most detailed views to date of the relationship between oral microbes, bacterial function, and host metabolism in MS. The results expand our understanding of MS beyond the gut and brain and highlight the mouth as another important site of immune-microbial interaction.”

Because obtaining a sample of the oral microbiome is easier than sampling the gut microbiome, the authors suggest this finding could lead to a new, non-invasive diagnostic signature for MS, as well as open the door to the development of oral MS therapies.

Multiple sclerosis is an autoimmune disease that affects approximately 2.9 million people worldwide. Relapsing-Remitting Multiple Sclerosis makes up approximately 85% of cases.

There is currently no cure for MS, but there are treatments that can slow its progression. Lifespan depends on disease type, age at diagnosis and treatment. The average life expectancy of someone with RRMS is approximately 78 years old.