Streptococcal bacteria, normally found in the mouth, have been found in thrombi taken from the brain arteries of acute ischaemic stroke patients, suggesting a possible link.

The research may help explain associations found between gum disease and ischaemic stroke, and underlines the importance of good dental care for stroke prevention, the Finnish authors say.

In the study, the thrombi, extracted by mechanical thrombectomy of 75 patients (mean age 67) with acute ischaemic stroke, were examined by quantitative PCR, looking for bacterial DNA of species commonly found in the mouth.

The majority of the clots (84%) contained bacterial DNA, with 79% of all the thrombi testing positive for streptococcus, mainly of the Streptococcus mitis group, the authors reported in the Journal of the American Heart Association.