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The finding that the oral bacteria Streptococcus mutans, which is found in 10% of the population, is linked with hemorrhagic strokes is big. S. mutans is found in tooth decay or cavities (dental caries). The researchers found a link with cnm-positive S. mutans with both intracerebral hemorrhage (ICH) and also with cerebral microbleeds. Some risk factors for strokes have long since been known, such as high blood pressure and advanced age, but then there are those hemorrhagic strikes that don't seem to fit the norm, with no apparent risk factors. Well, apparently the presence of cnm-positive S. mutans is one. My understanding of what cnm-positive S. mutans means is S. mutans bacteria that carries the collagen-binding Cnm gene. This bacteria can be found in a person's saliva and in dental plaque, and swabs of both were taken for this study.

This study builds on other studies that find a link between the bacteria Streptococcus mutans and a number of systemic diseases, including bacteremia, infective endocarditis and hemorrhagic stroke. The researchers of this latest study suggest that infection with cnm-positive S. mutans causes constant inflammation (as shown by 2 inflammatory markers: CRP and fibrinogen), which then causes damage to blood vessels (endothelial damage) in the brain. Bottom line: take care of your teeth and gums. From Science Daily:

Oral bacteria linked to risk of stroke

In a study of patients entering the hospital for acute stroke, researchers have increased their understanding of an association between certain types of stroke and the presence of the oral bacteria (cnm-positive Streptococcus mutans).

In the single hospital study, researchers at the National Cerebral and Cardiovascular Center in Osaka, Japan, observed stroke patients to gain a better understanding of the relationship between hemorrhagic stroke and oral bacteria. Among the patients who experienced intracerebral hemorrhage (ICH), 26 percent were found to have a specific bacterium in their saliva, cnm-positive S. mutans. Among patients with other types of stroke, only 6 percent tested positive for the bacterium.

Strokes are characterized as either ischemic strokes, which involve a blockage of one or more blood vessels supplying the brain, or hemorrhagic strokes, in which blood vessels in the brain rupture, causing bleeding.

The researchers also evaluated MRIs of study subjects for the presence of cerebral microbleeds (CMB), small brain hemorrhages which may cause dementia and also often underlie ICH. They found that the number of CMBs was significantly higher in subjects with cnm-positive S. mutans than in those without. The authors hypothesize that the S. mutans bacteria may bind to blood vessels weakened by age and high blood pressure, causing arterial ruptures in the brain, leading to small or large hemorrhages.

"This study shows that oral health is important for brain health. People need to take care of their teeth because it is good for their brain and their heart as well as their teeth," Friedland said. "The study and related work in our labs have shown that oral bacteria are involved in several kinds of stroke, including brain hemorrhages and strokes that lead to dementia."

Multiple research studies have shown a close association between the presence of gum disease and heart disease, and a 2013 publication by Jan Potempa, Ph.D., D.Sc., of the UofL School of Dentistry, revealed how the bacterium responsible for gum disease worsens rheumatoid arthritisThe cnm-negative S. mutans bacteria is found in approximately 10 percent of the general population, Friedland says, and is known to cause dental cavities (tooth decay). Friedland also is researching the role of oral bacteria in other diseases affecting the brain. http://www.nature.com/articles/srep20074

Another inadvertent way to kill off good bacteria. From the January 27, 2014 Medical Daily:

Antiseptic Mouthwash Raises Heart Attack Risk, Blood Pressure: Chlorhexidine Kills Off 'Good' Bacteria That Helps Blood Vessels Relax

Antiseptic mouthwash is commonly used to quickly refresh and clean the mouth after brushing your teeth in the morning, after eating, and before going to bed. According to a recent study published in the journal Free Radical Biology and Medicine, using a mouthwash twice daily — such as Corsodyl — may increase blood pressure up to 3.5 millimeters of mercury (mmHg), raising your heart attack risk.

Now a team of researchers at Queen Mary University of London believe using antiseptic mouthwash daily could increase the odds of HBP (high blood pressure) due to a chemical that kills the “good” bacteria responsible for helping the blood vessels relax.

Professor Amrita Ahluwalia, lead author of the study, and her team of researchers, observed the effects of a chlorhexidine-based antiseptic mouthwash — Corsodyl — by measuring the blood pressure of a small cohort of healthy participants during a two-week period. Chlorhexidine is an antiseptic that treats gingivitis and others problems of the mouth and gums. A total of 19 participants were recruited for the study during an initial seven-day control period followed by a seven-day treatment period with the antiseptic mouthwash. 

The findings revealed Cordosyl use retracts the oral bacterial conversion from nitrate to nitrate which reduces the plasma nitrate levels that are associated with increases in blood pressure. The mouthwash led the participants’ blood pressure to rise between 2 to 3.5 mmHg, with a noticeable effect found within one day of using the mouthwash twice.

The study authors believe killing off “good” oral bacteria plays a vital role in determining the plasma nitrate levels, and the bodily control of blood pressure. “Killing off all these bugs each day is a disaster, when small rises in blood pressure have significant impact on morbidity and mortality from heart disease and stroke,” said Ahluwalia, the Daily Mail reported. However, she adds, “We are not telling people to stop using antiseptic mouthwashes if they have a gum or tooth infection — but we would ask why anyone else would want to.”

The findings of the study do not apply to all mouthwashes because not all mouthwashes contain the chemical chlorhexidine, such as the popular Listerine. The study authors caution other mouthwashes could still produce the same effects as Corsodyl by damaging the mouth’s healthy bacteria.