London: Mouth bugs seeping into the bloodstream can cause blood clots and trigger endocarditis or inflammation of heart's inner tissues, which could be fatal.

Infective endocarditis is treated with surgery or by strong antibiotics - which is becoming more difficult with growing antibiotic resistance.

"About 30 percent of people with infective endocarditis die and most will require surgery for replacement of the infected heart valve with a metal or animal valve," said Helen Petersen from the Royal College of Surgeons in Ireland (RCSI) who led the study.

Streptococcus gordonii is a mouth bug which contributes to plaque formation on teeth. If they enter the blood stream through bleeding gums, they can wreak havoc by impersonating as human proteins.

Researchers from the RCSI and the University of Bristol have discovered that S. gordonii is able to produce a molecule on its surface that lets it mimic the human protein fibrinogen - a blood-clotting factor.

This activates the platelets, causing them to clump inside blood vessels. These unwanted blood clots encase the bacteria, protecting them from the immune system and from antibiotics that might be used to treat, according to a Royal College statement.

Platelet clumping can lead to growths on the heart valves (endocarditis), or inflammation of blood vessels that can block the blood supply to the heart or brain.

"Our team has now identified the critical components of the S. gordonii molecule that mimics fibrinogen, so we are getting closer to being able to design new compounds to inhibit it. This would prevent the stimulation of unwanted blood clots," said Steve Kerrigan from the RCSI.

These findings were presented at the Society for General Microbiology's Spring Conference in Dublin this week.