A mouthful of warning

HL: A mouthful of warning

Strap: New research shows oral bacteria weaken gut barriers, potentially worsening chronic liver disease outcomes

OB Bureau

A new study has found that bacteria living in the mouth can significantly influence gut health and even help predict the risk and progression of chronic liver disease, a condition that claims more than two million lives globally every year.

The research, published in the journal Nature Microbiology, analysed saliva and stool samples from 86 patients and uncovered a striking biological shift as liver disease worsens. Scientists from the Technical University of Munich (TUM) found that while healthy individuals have clearly distinct bacterial communities in different parts of the body, that separation begins to collapse in people with liver disease.

As the illness progresses, the oral and gut microbiomes start to resemble each other, with researchers recovering nearly identical bacterial strains from both the mouth and the intestines of affected patients. Crucially, changes in the oral microbiome were detectable at much earlier stages of the disease, long before severe damage set in.

“These strains are typically found in the mouth and are rarely present in the healthy gut,” said Melanie Schirmer, Professor of Translational Microbiome Data Integration at TUM. “However, we observed increases in the absolute abundance of these oral bacteria in patients with advanced chronic liver disease.”

“This strongly suggests that these bacteria translocate from the mouth and colonise the gut,” she added.

The study identified several oral bacterial species that had successfully settled in patients’ guts. Higher levels of these bacteria in stool samples were also linked to damage to the intestinal barrier — a critical line of defence that keeps harmful microbes from entering the bloodstream.

Gene analysis revealed another worrying detail – the bacteria carried genes that produce collagen-degrading enzymes. Laboratory tests confirmed these enzymes were active.

“Collagen breakdown can compromise the gut barrier, potentially allowing bacteria and bacterial products to reach other organs, such as the liver,” explained Aurelie Cenier, a doctoral researcher and co-first author. “We believe this may worsen the disease.”

The findings could reshape how doctors approach chronic liver disease. According to Dr Vishal Patel of King’s College London, targeting the oral microbiome and strengthening the gut barrier may offer new therapeutic paths. “Protecting or restoring the gut barrier could help slow disease progression,” he said. “Influencing oral bacteria may prevent complications before they spiral.”

In short, what’s happening in the mouth may hold the key to protecting the liver — and saving lives.