Two oral bacteria have been found in arterial plaque, according to a study published in the March issue of the American Heart Association’s journal Atherosclerosis, Thrombosis and Vascular Biology.
Scientists have found remnants of oral bacteria’s DNA in arteries, which signaled that bacteria had entered the bloodstream. However, scientists have not been able to grow periodontal bacteria isolated from arterial plaque in Petri dishes, even though the same species of bacteria swabbed from oral plaque can be cultured in Petri dishes. As a result, they could not be sure that the DNA was from oral bacteria destroyed by the immune system in the bloodstream, or if live oral bacteria were involved directly in arterial plaque formation.
To find bacteria that are infectious to both the oral and vascular tissues, Ann Progulske-Fox, Ph.D., a professor of oral biology at the University of Florida College of Dentistry, and colleagues attempted to grow bacteria from arterial plaque directly on human artery cells. They obtained a section of a diseased carotid artery from a 74-year-old, partially edentulous man who was undergoing surgery to remove an arterial blockage. After the arterial section was removed, researchers rinsed it, placed it on ice and took it to Dr. Progulske-Fox’s nearby laboratory in a sealed, sterile container.
Within six hours of the sample’s leaving the operating room, researchers pureed plaque from the artery and incubated it with a mixture of healthy arterial cells and liquid growth medium. After 24 hours, researchers separated the cells from the slurry in the flask, washed them several times, and subjected them to a series of fluorescent baths containing antibodies sensitive to Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans.
Using a microscope, researchers searched for the presence of invasive periodontal bacteria within the cells’ structures. The fluorescent antibodies lit up any artery cells infected with the bacteria.
Dr. Progulske-Fox and her team found that the endothelial cells were infected with both P. gingivalis and A. actinomycetemcomitans, which proved that live bacteria had been present in the atherosclerotic plaque. "Our finding is important because it has proved there are live periodontal bacteria in human atherosclerotic tissue," said Dr. Progulske-Fox.
She plans to study atherosclerotic tissue samples from 50 to 60 more patients to better understand how bacteria infect arterial cells. "More study samples will show us which strains are implicated in the disease process, so we can design simple diagnostic technology that could be used in a dental office to identify specific bacteria the patient is carrying and whether that bacteria is known to cause atherosclerotic disease," she said.
