Bacteria in mouth, gut bad for heart?

CORNELL (US) — The same types of bacteria found in plaques that play a role in heart disease also are found in the mouth and gut.

The findings come from the first general survey of all bacteria found in plaques from the mouth, gut, and blood. Details are reported in the Proceedings of the National Academy of Sciences,

“Our survey shows that bacteria are pretty good at getting out of the mouth and gut and into the blood stream,” says Ruth Ley, Cornell University assistant professor of microbiology and a senior author of the study with Frederik Bäckhed, a cardiovascular researcher from the University of Gothenburg.

The study used samples from the mouth and feces (to determine bacteria in the gastrointestinal tract) from 15 heart disease patients who had plaque removed from their arteries. Samples were also taken from a control group of 15 healthy individuals who matched the heart disease patients by sex and age.

The findings show that such bacteria as Veillonella and Streptococcus were the most abundant microbiota found in plaque. Furthermore, when a lot of these two types of bacteria were found in the mouth, the researchers found a corresponding abundance of the same bacteria in the arterial plaque.

Previous studies have provided evidence that bacteria from the mouth and gut may play a role in the formation of arterial plaque, leading to coronary disease. Studies have shown that mice, whose immune systems were compromised in such a way that they could not detect bacteria, were resistant to atherosclerosis, leading researchers to suspect that arterial plaque forms partly due to the body’s immune reactions to bacteria.

In atherosclerosis, plaque collects along the walls of arteries, where it thickens, hardens (forming calcium deposits), and may eventually block the arteries.

Ley and colleagues found a positive correlation between amounts of bacteria and leukocytes (white blood cells) in arterial plaque, supporting the theory that higher levels of arterial plaque lead to an immune response and inflammation.

Also, Chryseomonas bacteria were found in all samples of atherosclerotic plaque, suggesting that the bacteria may contribute to its development. Also, Streptococcus in the mouth and gut were positively correlated with HDL (“good”) cholesterol, while a number of other gut bacterial were positively correlated with LDL (“bad”) and total cholesterol.

The study, which used high throughput DNA sequencing techniques to get more comprehensive data than in previous research, was funded in part by the Swedish Research Council, National Institutes of Health, and National Science Foundation.

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