Around the globe, heart disease remains a leading cause of death. According to the World Health Organization, nearly 20 million people died from heart disease in 2022, with a staggering 85% of these deaths resulting from strokes and heart attacks. A heart attack, known medically as a myocardial infarction, occurs when the blood supply to the heart is blocked. This blockage can stem from various causes, including blood clots, a spasm of the coronary artery, or, most commonly, the buildup of plaque—a substance partially composed of cholesterol—on the inside walls of the arteries. This process, known as atherosclerosis, leads to coronary artery disease.
For a long time, research has suggested that infections, particularly those from bacteria that enter the bloodstream, could be a risk factor for heart disease. Studies have also pointed to a connection between bacterial infections and an increased risk of arterial plaque formation. While this theory was considered and largely set aside decades ago, recent advances in molecular microbiology have reignited interest.
Dr. Pekka J. Karhunen, a professor at Tampere University in Finland, has been at the forefront of this renewed inquiry. He explains that for many years, the possibility of infectious agents being involved in the chronic inflammation of coronary plaques was a topic of discussion. However, the theory was put on hold after large-scale, long-term antibiotic trials failed to show a significant impact on heart disease. Now, with the ability to identify bacterial DNA in even tiny biological samples, the scientific community is taking a second look.
Dr. Karhunen is the lead author of a new study published in the Journal of the American Heart Association that suggests bacteria commonly found in the mouth and throat may directly trigger a heart attack. To explore this, the researchers examined coronary plaque samples from two groups of people: 121 individuals who had died from sudden cardiac arrest and 96 people who underwent an endarterectomy, a surgical procedure to clear plaque from their arteries.
bacterial infections and heart disease
The study’s findings were compelling. The most prevalent bacteria found in the coronary plaque samples belonged to the viridans group Streptococci. This is a broad category of Streptococcus bacteria that are naturally present in saliva and dental plaque. Dr. Karhunen noted that these bacteria are known to be some of the first to colonize in the formation of dental plaque, which suggests they may not be acting alone, but as part of a larger bacterial community, or biofilm.
He explained that within a bacterial biofilm, the bacteria are protected by a gel-like covering, and in this state, they typically do no harm. However, the situation can change dramatically if the biofilm is activated. When this happens, new generations of bacteria can break out and infiltrate the atherosclerotic plaque. This infiltration can cause inflammation, which may lead to the plaque rupturing. A ruptured plaque can then result in the formation of a blood clot, or thrombus, which can cause a heart attack.
The researchers plan to continue their work to better understand the role of these biofilms. They are exploring whether the calcification of these biofilms—a process that also happens with dental plaque—could be linked to the calcification of coronary arteries. They are also investigating the potential for a vaccine to prevent the formation of these biofilms and the bacterial-induced thrombosis they can cause.
According to Dr. Sergiu Darabant, a cardiologist at Miami Cardiac & Vascular Institute who was not involved in the research, these findings are intriguing but not entirely unexpected. He stated that inflammation has long been suspected as a major factor in the formation and rupture of cholesterol plaques. This study, he said, “adds another piece to the puzzle” by illustrating how mouth bacteria could be a “hidden driver of coronary inflammation.”
Dr. Darabant believes that identifying these types of triggers—such as transient bacteremia or respiratory infections—could lead to new, targeted therapies that would complement existing medications for managing cholesterol, blood pressure, and diabetes.
Dr. Yu-Ming Ni, a board-certified cardiologist and lipidologist, also commented on the study, calling the implication of strep viridans in atherosclerosis “interesting.” However, he cautioned that such studies have limitations because they provide a snapshot after the fact, making it difficult to establish a precise timeline of events leading up to the vascular event. Despite this, the research highlights a significant and previously underestimated link between oral health and the health of the heart.
