This unusual bacterial migration, known as “oral-gut translocation,” indicates that microbes from the mouth are travelling into the gut where they do not naturally belong
Harmful bacteria found in the mouth and gut may accelerate cognitive decline in people with Parkinson’s disease, a new study has revealed, opening up new possibilities for early diagnosis and treatment of the neurodegenerative condition.
Conducted by researchers at King’s College London, the study provides compelling evidence that shifts in the body’s microbiome — the community of microorganisms living in the gut and oral cavity — are associated with the progression of Parkinson’s-related dementia.
The research, published in the journal Gut Microbes, indicates that specific bacteria, especially those migrating from the mouth to the gut, may be triggering inflammation and producing toxins that damage brain function.
“Disruptions in the gut-brain axis could trigger inflammation and immune responses that contribute to neuronal damage,” explained Dr Saeed Shoaie, lead author and head of the Quantitative Systems Biology Lab at King’s College. “The human gut and oral bacterial communities are increasingly being linked to neurodegenerative diseases.”
To investigate the relationship between bacteria and Parkinson’s symptoms, the researchers collected and analysed 228 samples of stool and saliva. The study focused on two groups of Parkinson’s patients — those experiencing mild cognitive impairment and those already diagnosed with dementia — and compared them with a healthy control group.
The results revealed significant differences in the composition and behaviour of microbes between the Parkinson’s and non-Parkinson’s participants. In particular, those with cognitive symptoms had higher levels of harmful bacteria in their gut, many of which are typically found in the mouth.
This unusual bacterial migration, known as “oral-gut translocation,” indicates that microbes from the mouth are travelling into the gut where they do not naturally belong.
These invaders were found to produce virulence factors — toxic molecules that can damage intestinal tissues, promote systemic inflammation, and potentially influence brain function.
“We don’t yet know whether these bacteria are directly causing the cognitive decline or if Parkinson’s-related changes in the body are allowing them to grow,” said Dr Frederick Clasen, research associate at King’s and co-author of the study. “But our findings strongly suggest they may play an active role in worsening symptoms.”
To enhance their findings, the team used artificial intelligence (AI) to analyse bacterial species and their function more accurately. The AI identified specific toxins linked to cognitive decline — discoveries that may not have been possible using traditional microbiology methods.
“These toxins could eventually be used as biomarkers to identify which patients are more likely to develop dementia as their Parkinson’s progresses,” Dr Clasen added. “They might also serve as targets for new therapies that protect the brain by altering the gut microbiome.”
The research highlights a critical, and often overlooked, aspect of Parkinson’s care: oral hygiene and digestive health. As the disease advances, maintaining microbial balance in the mouth and gut could prove essential for slowing down cognitive decline.
With Parkinson’s notoriously difficult to diagnose early, especially in cases where memory loss is subtle or delayed, this study provides hope for future non-invasive testing tools and preventative treatment strategies.
