- In 2022, about 19.8 million people globally died from heart disease, with about 85% of these deaths attributed to stroke and heart attack.
- Previous research has linked bacterial infections as a risk factor for heart disease.
- Past studies have also linked bacterial infections to an increased risk of arterial plaque buildup.
- A new study has now identified specific bacteria typically found in the mouth and throat, which researchers believe may be a trigger for a heart attack.
Medically known as myocardial infarction, a heart attack occurs when blood in the arteries is blocked from being able to reach the heart.
Previous research has linked
Pekka J. Karhunen, MD, PhD, a professor in the Faculty of Medicine and Health Technology at Tampere University in Finland, told Medical News Today that:
“The possibility that infectious agents are involved in the chronic inflammation of coronary plaques has been considered for a long time, but this theory was abandoned about 20 years ago due to failed large long-term antibiotics trials. The interest has now been renewed due to the development of molecular microbiological methods that enable the identification of bacterial DNA even in small amounts of biological specimens.”
Karhunen is the first author of a new study recently published in the
For this study, researchers analyzed coronary plaque samples from 121 people who had died from sudden cardiac death, and from 96 people who had undergone surgery to have the plaque from their arteries cleaned, a procedure known as an endarterectomy.
At the study’s conclusion, the scientists discovered that the bacteria viridans group Streptococci — an umbrella-term for types of Streptococcus bacteria commonly found in the mouth, in saliva and dental plaque — were the most common bacteria in the coronary plaque samples.
“Oral viridans group Streptococci are known to act as early colonizers in the buildup of the dental biofilm known as dental plaque,” Karhunen explained. “This signals that the streptococci may not be there alone — it is possible that there is a biofilm composed of many bacteria. In fact we have unpublished results confirming this.”
“In the bacterial biofilm, the bacteria are safe inside the jelly-like cover and they do not cause any harm to the individual,” he continued.
However, he noted, “the situation changes dramatically when the biofilm activates for [some] reason or other, and starts to produce new generation of bacteria that break out from the biofilm and infiltrate the atherosclerotic plaque, causing inflammation that can rupture the plaque ending up in the formation of a thrombus.”
“We aim to show that there is a biofilm consisting of many bacteria in the atherosclerotic plaques and we also study the possibility that calcification of the biofilm — which occurs in the surface of the teeth — might also be involved in the calcification of coronary arteries,” Karhunen added. “We also studied the possibility of developing a vaccine against the formation of a biofilm and bacterial-induced thrombosis.”
MNT spoke with Sergiu Darabant, MD, a cardiologist with Miami Cardiac & Vascular Institute, part of Baptist Health South Florida, about this study, who said he did not find the study surprising, but intriguing.
“We’ve long suspected that inflammation is a key driver of cholesterol plaque formation and plaque rupture leading to heart attacks,” Darabant, who was not involved in the research, said. “This study adds another piece to the puzzle — showing how bacteria from the mouth might play a hidden role in driving coronary inflammation.”
“Even though we’ve made significant progress over the years in the advancement of medical therapies aimed at cardiovascular risk reduction and secondary prevention of cardiovascular events, our prevention toolkit is still limited,” he continued.
MNT also spoke with Yu-Ming Ni, MD, a board-certified cardiologist and lipidologist at MemorialCare Heart and Vascular Institute at Orange Coast Medical Center in Fountain Valley, CA, likewise not involved in the study, about these research findings.
“This bacteria, strep viridans, is a very common oral bacteria, and the fact that it seems to be implicated in atherosclerosis is interesting,” Ni commented.
However, he cautioned that “it’s important to recognize that these studies have some limitations because you’re taking a picture in the aftermath, so you don’t have a great timeline for what exactly is happening in someone’s plaque that leads them to have this vascular event.”
“So I would be cautious to just go and make the assumption that these bacteria are definitely the reason for plaque disruption. I think there’s maybe more to that than just that, but it does support the idea of inflammation as a key factor in the development of clinical heart disease.”
– Yu-Ming Ni, MD
When hearing the term “bacterial infection,” there may be worry that you could also be at risk of acquiring it.
Brett A. Sealove, MD, FACC, FAHA, RPVI, CPE, chair of cardiology at Hackensack Meridian Jersey Shore University Medical Center, and associate professor and vice chair of cardiology at Hackensack Meridian School of Medicine in New Jersey, told MNT people need not immediately worry about strep viridans, as these bacteria are typically benign, and help maintain a healthy balance in the mouth and body.
“These bacteria live synergistically within the human body, most abundantly in the oral cavity as well as the respiratory and gastrointestinal tracts,” Sealove detailed.
“However,“ he explained, “problems arise when they enter the body — mostly via the mouth — and can cause other infections, most notably an infection of heart valves, called endocarditis. So, they are benign and normally found in the body. It’s their displacement and travel that can potentially cause harm.”
There is no vaccine approved for strep viridans, Edward Liu, MD, MPH, FACP, FIDSA, chief of infectious diseases at Hackensack Meridian Jersey Shore University Medical Center in New Jersey told MNT.
“Strep viridans is common and expected to be in parts of the body, especially the mouth,” Liu explained. “I would not expect other strep vaccines — for example, strep pneumonia vaccines like pneumovax or prevnar 13 or 20 — to protect against strep viridans.”
Liu recommended treating any active infections in a timely manner, as they occur:
“For example, a dental infection may likely include strep viridans as well as other bacteria found in the mouth. We know that severe dental infections can lead to bacteria in the blood, so timely treatment of dental infections could be beneficial.”
Speaking of dental care, Sealove said that optimizing one’s oral hygiene and seeking dental treatment where necessary is a way to help people protect themselves from bacterial infections that may lead to heart attack.
“The oral-systemic link is backed by an abundance of growing evidence, and very much supported by this article, which focuses on the connection between oral and systemic health,” he explained. “The mouth provides function and aesthetics but also is an active ecosystem which needs to be healthy, and can impact one’s systemic health — especially the cardiovascular system.”
“These reduce risk of severe infections, which have been associated with cardiovascular events, especially in high-risk and post-myocardial infarction patients,” he added.