Mouth germs can trigger blood clots

Bugs escaping from the mouth employ a survival trick that can trigger deadly blood clots, research has shown.

The link between bacteria that cause dental plaque and heart disease and strokes is well known.

Scientists have now discovered just why it is that the microbes pose a far bigger risk than receding gums.

Once let loose in the bloodstream they deploy a protein that forces platelets to bind together and shield the bugs with clots.

Study leader Professor Howard Jenkinson, from the University of Bristol, said: "When the platelets clump together they completely encase the bacteria.

"This provides a protective cover not only from the immune system, but also from antibiotics that might be used to treat infection.

"Unfortunately, as well as helping out the bacteria, platelet clumping can cause small blood clots, growths on the heart valves, or inflammation of blood vessels that can block the blood supply to the heart and brain."

Speaking at the Society for General Microbiology's autumn meeting in Nottingham, Prof Jenkinson said oral bacteria can "wreak havoc" if not kept in check by regular brushing and flossing.

"Poor dental hygiene can lead to bleeding gums, providing bacteria with an escape route into the bloodstream, where they can initiate blood clots leading to heart disease," he said.

The Streptococcus bacteria normally live in confined communities in the mouth called biofilms. It is these that are responsible for dental plaque and gum disease.

The bugs become far more potentially harmful once they break free of the mouth and enter the blood circulation.

"People need to be aware that as well as keeping a check on their diet, blood pressure, cholesterol and fitness levels, they also need to maintain good dental hygiene to minimise their risk of heart problems," said Prof Jenkinson.

The team is using a new blood flow model developed by the Royal College of Surgeons in Ireland that mimics conditions inthe human circulatory system.

The scientists are investigating how the platelet-activating behaviour of Streptococcus bacteria can be blocked.

"This could eventually lead to new treatments for cardiovascular disease, which is the biggest killer in the developed world," said Prof Jenkinson.

:: Clever survival tactics are also employed by food-poisoning Listeria bugs, the meeting was told.

The bacteria, found in soft cheeses and chilled ready meals, are able to overcome harsh acidic conditions by exploiting key food ingredients.

Certain food constituents such as the amino acid glutamate allow the bugs to neutralise acid, allowing them to pass through the stomach unscathed.

"People who consume foods that are contaminated with Listeria and are also high in glutamate, such as soft cheese or meat products, have a higher chance of developing serious infection than someone eating the same quantity of bacteria in a low-glutamate food," said Professor Colin Hill, from University College Cork in the Irish Republic.

Food processing and storage conditions can also help Listeria to become more acid-tolerant, he added.