The Bacteria That Causes Multiple Sclerosis Has Been Found.

Source: PMC PubMed Central

Multiple Sclerosis and the Gut Microbiome: What Researchers Are Learning

Researchers are continuing to investigate the connection between the gut microbiome—the community of microorganisms living in our digestive system—and multiple sclerosis (MS).

A 2025 study published in Proceedings of the National Academy of Sciences (PNAS) examined the gut microbiota of 81 pairs of identical twins in which one twin had MS and the other did not. Studying genetically identical twins allowed researchers to reduce some of the genetic and early-life factors that can make it difficult to identify potential differences associated with MS.

The researchers found more than 50 differences in the abundance of specific types of gut bacteria between the twins. They then took samples from different areas of the digestive tract, including the ileum (the final section of the small intestine), and introduced these microbiota samples into specially bred germ-free mice that are susceptible to an MS-like autoimmune disease.

The results showed that mice receiving microbiota from the ileum of people with MS developed the MS-like disease at higher rates than mice receiving microbiota from their healthy twin counterparts.

Researchers identified two groups of bacteria within the Lachnospiraceae family—Eisenbergiella tayi and Lachnoclostridium—as possible contributors to the increased disease activity observed in the mice.

These findings add to growing research suggesting that the gut-brain connection and gut microbiome may play a role in the immune processes involved in MS. However, it is important to note that this study does not prove that these bacteria cause MS in people. The disease-related effects were observed using an experimental mouse model, and additional research is needed to understand whether and how these findings translate to humans.

Understanding the relationship between the gut microbiome and MS could ultimately help researchers learn more about how the disease begins and develops and may open new avenues for future research and potential treatments.