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Study Links Bacteria to Strokes


A type of bacteria previously linked to ulcers may also be a key factor in some strokes, according to a study that lends support to the theory that infections and inflammation play a role in heart attacks and strokes.

Previous studies looking for a connection between Helicobacter pylori, the cause of most stomach ulcers, and stroke were inconclusive. But a new study scheduled to appear in the July 30 issue of Circulation: Journal of the American Heart Assn. suggests that particularly virulent strains of H. pylori can invade and damage arteries and potentially lead to a stroke.

Researchers led by Dr. Antonio Pietroiusti, an internist at the Tor Vergata University in Rome, found that H. pylori strains that produce potent poisons, called cytotoxins, were more prevalent in the blood of patients who suffered strokes caused by narrowing of arteries in the neck and brain. These cytotoxins are thought to attack plaque-lined artery walls, causing inflammation and swelling, creating an environment for a stroke.

Every year, 750,000 Americans suffer a stroke and 160,000 die, making strokes the third-leading cause of death in this country. They occur either when a blood clot forms inside a blood vessel and cuts off blood flow to the brain, killing cells, or when a blood vessel breaks.

The researchers examined strains of H. pylori in the blood of 138 patients who suffered strokes in plaque-lined vessels leading to the brain, and 61 patients whose strokes were caused by clots that formed in the heart and traveled to the brain. They compared both those groups to 151 healthy volunteers.

Although members of all three groups showed equivalent amounts of H. pylori in general, the significant finding was that 42.8% of people with large-vessel strokes had strains of the cytotoxin-producing bacteria, compared with 19.7% of those whose strokes had cardiac origins, and 17.9% of healthy volunteers.

Because the study was a so-called case control study, it only was able to find an association between the bacteria and strokes; it could not prove H. pylori caused the strokes. But researchers found other evidence of the link between some H. pylori and strokes. Levels of C-reactive protein, which measure inflammation, were higher in both stroke groups than in healthy volunteers. They were significantly higher in patients with the cytotoxin-releasing H. pylori, suggesting the bacteria cause the inflammation.

The study is important because it's more evidence showing the association of infection, atherosclerosis and stroke, said Dr. Ravinder Singh, a Beverly Hills neurologist who specializes in stroke. "It probably is not going to change the way we manage patients. But hopefully it will lead to other prospective studies ... that would look at whether this is a cause of atherosclerosis and if it is, how can we prevent it?"

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