A groundbreaking study presented at the 2025 American Stroke Association International Stroke Conference has revealed a potential link between Streptococcus anginosus, a common bacterium found in the mouth and gut, and an increased risk of stroke.
Study Findings: Bacteria and Stroke Risk
Research conducted in Japan examined stroke survivors and found that those with higher levels of S. anginosus were more likely to suffer a major cardiovascular event or die within two years of their stroke. The study, which analyzed saliva and stool samples from 250 participants (189 stroke patients and 55 non-stroke individuals), indicated that the bacterium was independently associated with a 20% higher stroke risk. Conversely, a beneficial gut bacterium was linked to an 18% reduced risk.
Oral Health and Stroke Prevention
S. anginosus is known to contribute to tooth decay by producing acids that erode enamel. Experts suggest that maintaining proper oral hygiene, reducing sugar intake, and using specialized toothpaste targeting this bacterium may not only prevent dental issues but also potentially reduce stroke risk.
Expert Insights
Dr. Louise D. McCullough, chief of neurology at Memorial Hermann Hospital-Texas Medical Center and co-director of UTHealth Neurosciences, emphasized the significance of these findings. "Poor oral health can lead to inflammation and may increase stroke risk. The increased levels of S. anginosus found in the gut of stroke patients are intriguing, especially considering their link to higher mortality two years post-stroke."
Lead author Dr. Shuichi Tonomura from Osaka's National Cerebral and Cardiovascular Center highlighted the potential for early detection. "If a quick test could identify harmful bacteria in the mouth and gut, we might better calculate stroke risk. Lifestyle strongly influences the microbiome, so other bacteria could play similar roles in different populations."
Future Research and Implications
While the findings are compelling, experts caution that larger studies are needed to confirm the association between S. anginosus and stroke. Researchers plan to extend their study to individuals without a history of stroke but with significant risk factors. Dr. McCullough and her team believe this approach could provide deeper insights into stroke prevention and microbiome-related health strategies.