Study Connects Gum Germ to Brain Disease

A groundbreaking study led by researchers in South Korea claims to be the first to describe a direct microbial mechanism connecting an oral bacterium to Parkinson’s disease. The investigation, published in Nature Communications, found that Streptococcus mutans—a bacterium commonly associated with dental decay—was present in the gut microbiome of individuals with Parkinson’s and may actively contribute to neuronal damage in the brain.

The research team analyzed stool samples from about 500 Parkinson’s patients and 234 healthy controls, constructing high-resolution gut microbiome profiles. They discovered that S. mutans produces an enzyme called UrdA, which leads to the formation of a metabolite named imidazole propionate. This metabolite, according to their experiments, is capable of crossing into the central nervous system and harming dopamine-producing neurons, a hallmark feature of Parkinson’s disease.

To test causality, the researchers introduced either S. mutans or imidazole propionate into mice models. The animals developed motor impairments and brain changes consistent with Parkinsonian pathology—providing experimental evidence that this pathway could contribute to disease onset.

What makes this finding remarkable is that it suggests a gut–brain axis mediated by an oral microbe, linking the mouth, digestive tract, and neurological system. Previous studies had only established associations between microbiomes and neurological changes, but this work attempts to trace a specific bacterial species and metabolite to neuronal damage.

Of course, the authors and commentators caution that this is still early research. While the experiments in mice show promising proof-of-concept, human biology is far more complex. Whether S. mutans colonization in the gut or its metabolite consistently contribute to Parkinson’s risk in people remains to be further verified by longitudinal, mechanistic human studies.

If the results hold up, this research opens up new possibilities: interventions targeting oral bacteria (through improved oral hygiene, targeted antimicrobials, or microbiome modulation) could become part of strategies to reduce Parkinson’s risk or slow its progression.

📖 Original Article Info

“‘First’ study links oral bacteria to Parkinson’s disease.”

Oral Health Group, September 26, 2025