We now need to investigate if these bacteria are important players
In the quiet interior of the human body, a community of microbes may be quietly shaping the fate of the heart. Swedish researchers, drawing on one of the world's most comprehensive biological datasets, have found that certain gut bacteria — particularly species of Streptococcus long known for causing infection — are associated with the early buildup of fatty plaques in the coronary arteries of nearly 9,000 middle-aged adults. The discovery does not yet tell us whether these bacteria are architects of disease or merely witnesses to it, but it opens a door between the microbial world and cardiovascular medicine that science is only beginning to walk through.
- Streptococcus bacteria typically associated with throat and heart valve infections have now been found linked to arterial plaque buildup in the hearts of thousands of otherwise healthy adults.
- The same bacterial species appeared in both the gut and the mouth of participants, suggesting the body's microbial communities are more interconnected — and more consequential — than previously understood.
- Elevated blood inflammation markers were found in people carrying these bacteria, independent of diet or medication, intensifying the suspicion that something biological and systemic is at work.
- The critical unanswered question — whether these bacteria cause atherosclerosis or simply accompany it — is now driving the next phase of research.
- If causality is confirmed, entirely new preventive strategies could emerge, from targeted oral hygiene interventions to probiotics or precision antimicrobial therapies.
Swedish researchers have drawn a striking line between the bacteria living in the human gut and the fatty plaques that accumulate in the arteries of the heart. The finding comes from a large-scale study of nearly 9,000 middle-aged adults with no prior heart disease, all part of the Swedish CArdioPulmonary bioImage Study — one of the world's most detailed efforts combining bacterial DNA analysis with advanced cardiac imaging.
The two bacterial species at the center of the discovery, Streptococcus anginosus and Streptococcus oralis subspecies oralis, are familiar agents of human infection, known to cause pneumonia, throat infections, and even heart valve disease. Their appearance in association with early coronary artery plaques pointed toward a previously unrecognized pathway connecting the microbial world to cardiovascular risk.
What deepened the intrigue was evidence that these bacteria were not acting in isolation. Analysis of a separate group of participants revealed the same species present in both gut and mouth, suggesting a biological bridge between oral and intestinal microbiota. People carrying these streptococci also showed elevated inflammation markers in their blood — a known precursor to heart disease — even after accounting for differences in diet and medication.
Lead author Sergi Sayols-Baixeras credited the unprecedented scale of the dataset for making these connections visible, while senior author Marju Orho-Melander was careful to note that association is not yet causation. Whether these bacteria actively drive plaque formation or simply reflect some deeper underlying vulnerability remains the defining question. The answer could reshape preventive cardiology — but for now, science has identified a new corner of the microbial map worth exploring.
Swedish researchers have identified a connection between specific bacteria living in the human gut and the buildup of fatty plaques in the arteries of the heart. The discovery emerged from a large-scale study of nearly 9,000 middle-aged adults and was published in the journal Circulation, marking a significant step toward understanding how the microscopic world inside our bodies influences cardiovascular risk.
The research team, led by scientists at Uppsala and Lund University, examined gut bacteria samples and heart imaging data from 8,973 participants between ages 50 and 64 who had no prior history of heart disease. All were part of the Swedish CArdioPulmonary bioImage Study, or SCAPIS, one of the world's largest collections combining detailed bacterial analysis with advanced cardiac imaging. The researchers used DNA sequencing to identify which bacteria were present in each person's digestive tract, then cross-referenced those findings with imaging that could detect early fatty deposits forming in the small vessels supplying the heart.
The strongest associations emerged with two species: Streptococcus anginosus and Streptococcus oralis subspecies oralis. These bacteria are well-known culprits in human infection—they commonly cause pneumonia, throat infections, skin infections, and even infections of the heart valves themselves. Finding them linked to atherosclerotic plaques in the coronary arteries suggested a previously unrecognized pathway by which oral bacteria might influence heart disease risk. The research team, coordinated by Tove Fall, a professor of molecular epidemiology at Uppsala University, noted that the sheer size and quality of the SCAPIS dataset made it possible to spot these associations that smaller studies might have missed.
What made the findings particularly intriguing was the evidence that these gut bacteria were not acting in isolation. When researchers examined saliva and stool samples from a separate group of participants in the Malmö Offspring Study, they found that the same bacterial species present in the gut were also detectable in the mouth. This suggested a biological connection between oral and intestinal microbiota. More striking still, people carrying these streptococci in their gut showed elevated inflammation markers in their blood—a known risk factor for heart disease—even after researchers accounted for differences in diet and medication use among participants.
Sergi Sayols-Baixeras, the lead author from Uppsala University, emphasized that the scale of the study allowed the team to identify novel connections that would have been invisible in smaller research efforts. The technological advances that made this work possible—both in DNA sequencing and in cardiac imaging—have only recently made such comprehensive analysis feasible. Researchers can now map bacterial communities with unprecedented precision and detect the earliest signs of arterial damage in ways that were impossible just a decade ago.
Yet the researchers were careful to frame their findings as a beginning rather than a conclusion. Marju Orho-Melander, a professor of genetic epidemiology at Lund University and senior author, noted that the study shows an association between these bacteria and worse cardiovascular health, but the causal direction remains unclear. Do these streptococci actively drive the development of atherosclerosis, or are they simply markers of some other underlying condition that increases heart disease risk? That question will shape the next phase of research. If the bacteria prove to be active contributors to plaque formation, the door opens to entirely new preventive strategies—potentially targeting oral hygiene, specific probiotics, or even targeted antimicrobial approaches. For now, the Swedish team has mapped a corner of the microbial landscape that influences the heart, and the field is watching to see what comes next.
Citas Notables
We found that oral bacteria, especially species from the Streptococcus genus, are associated with increased occurrence of atherosclerotic plaques in the small arteries of the heart when present in the gut flora.— Tove Fall, Professor of Molecular Epidemiology, Uppsala University
We now need to investigate if these bacteria are important players in atherosclerosis development.— Marju Orho-Melander, Professor of Genetic Epidemiology, Lund University
La Conversación del Hearth Otra perspectiva de la historia
So these bacteria live in the gut, but they're also found in the mouth. How do they get from one place to the other?
That's still being worked out. The study shows they're present in both locations, but the mechanism—whether they travel, whether they're the same strain, whether one location seeds the other—that's part of what needs investigation next.
If someone has these bacteria, does that mean they'll definitely develop heart disease?
No. The study found an association, not a guarantee. Some people carry these bacteria and remain healthy. Others don't carry them and still develop atherosclerosis. It's one piece of a much larger puzzle that includes genetics, diet, exercise, smoking, and dozens of other factors.
Why would bacteria that normally cause throat infections end up linked to heart plaques?
That's the central mystery. One possibility is that they trigger chronic inflammation in the gut or bloodstream. Another is that they produce compounds that damage blood vessel walls. Or they might be a marker of a disrupted microbiome that allows other harmful processes to unfold. The researchers are honest that they don't yet know.
Could you prevent atherosclerosis by eliminating these bacteria?
That's the hope, but it's premature. First, researchers need to establish whether these bacteria are actually causing the problem or just traveling alongside it. If they are causal, then yes—targeting them could become a prevention strategy. But if they're merely correlated with some other risk factor, eliminating them alone won't help.
What makes this study different from previous microbiome research?
The scale and the precision. Nearly 9,000 people with both detailed bacterial mapping and cardiac imaging. Most microbiome studies are smaller or lack the imaging data to show actual disease. This one connects the dots from bacteria to inflammation to visible arterial damage in a way that's hard to ignore.