The bug in question, Helicobacter pylori, causes ulcers, and has also been implicated in the development of stomach cancer and ischaemic heart disease.
The researchers base their findings on 59 patients with persistent atrial fibrillation. The patients included those who had no structural heart disease.
All the patients were given a battery of tests, including a heart tracing, and levels of C reactive protein, an indicator of systemic inflammation. They were also directly tested for the presence of H pylori.
The results were compared with those from a group of 45 healthy volunteers in whom the same tests were carried out.
Both groups were similar in terms of age and levels of blood fats, although significantly more of the patients with atrial fibrillation were being treated for high blood pressure.
The patients with atrial fibrillation were around 20 times as likely to test positive for H pylori as the healthy volunteers, and their levels of C reactive protein were around five times as high.
Both rates of H pylori and C reactive protein levels were also significantly higher among those patients with persistent atrial fibrillation than those with spasmodic episodes of irregular heart rhythm.
H pylori is a very resilient bacterium and has properties that enable it to escape detection by the immune system, say the authors. And chronic gastritis, caused by persistent H pylori infection, may predispose to atrial fibrillation, they suggest.