Bacteria That Cause Cavities Found to Increase Stroke Risk


If you’re like many Americans, you probably dread visits to the dentist. Whether you’re avoiding another lecture about how often you should be flossing or the whine of the dental drill for yet another root canal, going even once a year might seem too often. But new research published this week serves as a reminder for why good mouth care and regular visits to the dentist are so important and the findings might have you picking up that toothbrush or reaching for the floss a little more often than usual.

How does the health of our mouth affect our body?

While it might not seem obvious that keeping your teeth clean can lead to better health overall, many studies have linked oral health to lower risk of a variety of diseases. In particular, it seems as though the cardiovascular system (made up of the heart, arteries and veins) is potentially heavily influenced by what’s going on in your mouth. People with various oral health problems, like cavities or gum disease, also tend to have higher rates of diseases like stroke and heart disease. Unfortunately, most of the studies that have found these links weren’t designed to figure out how this is happening. Those studies that were aimed at pulling this link apart have found that it might be bad habits like smoking or unhealthy diets end up leading to both mouth problems and other health issues simultaneously. But some researchers suspected that there might be something going on in the mouth itself that could be playing a role in diseases like stroke.

Why are bacteria important in the mouth?

Bacteria are everywhere on our bodies, from our skin to our intestines to our bladder. The human mouth is well-known to be home to billions of bacteria, most of which are completely harmless and may even be helpful. But every now and then, a few bad apples are able to carve out a home in our mouths. A bacteria called Streptococcus mutans (or Strep mutans for short) is one of these nefarious characters. Strep mutans is one of the prime suspects for causing cavities because they thrive in the mouths of people with poor diets and poor oral hygiene. These bacteria set up shop in groups called “biofilms” often protected within the fissures of the molar teeth. They feed off of sugar in the mouth and produce acid that breaks down tooth enamel and allows the bacteria to burrow into the tooth and form a cavity.

What was different about this study of Strep mutans?

The research team had recently completed a study that found an association between tiny bleeds in the brain and the presence of Strep mutans in the mouth. The team had also done another study of a form of Strep mutans that was a little different from your run-of-the-mill version. It carried a gene called cnm that the researchers had shown potentially allowed the bacteria to bind to blood vessels of the brain and break them down, which might then lead to the types of strokes the researchers had seen in their other study. The team wanted to use this study to put in the final puzzle piece showing that Strep mutans with a cnm gene was linked to this specific kind of small stroke in the brain.

How did the researchers study the link between strokes and Strep mutans?

The research team identified 99 people in the hospital who had recently had strokes and tested their mouths for the presence of Strep mutans strains both with and without the cnm gene. They found the bacteria in 51 of the individuals. They then looked to see if the presence of this bacteria was associated with any one of the different types of strokes a person could have, including strokes related to bleeding versus a clot in the brain and the size of the stroke that occurred. Finally, they grew Strep mutans from the subjects that either had or didn’t have the cnm gene in the lab and looked to see whether their activity might correlate with the stroke information they had collected.

What did the researchers find?

The team found that being infected with Strep mutans that carried the special cnm gene made individuals more likely to have a stroke from a bleed in their brain coming from the small arteries that feed the deeper areas of the brain. These individuals were also more likely to have blood signs of inflammation, which the team thinks might reflect some of the damage the bacteria are doing to the blood vessels. The team also found that this more damaging strain of Strep mutans grown from the participants in the study was better able to grab onto the walls of blood vessels and to damage them than strains without the necessary gene. Based on this information, the researchers think strokes might happen this way:

  • Blood vessels start to weaken as a person ages, especially if they have damaging high blood pressure, making them more likely to break and bleed
  • Strep mutans gets into the bloodstream by making cavities in teeth and finding the blood vessels that normally feed teeth
  • Once in the blood stream, Strep mutans uses the Cnm protein to bind to these small, weak blood vessels in the brain and damages them further, which then leads to a small stroke
  • This damage also leads to inflammation around where the bacteria have attached, which can weaken the walls of the blood vessels even more and make future strokes more likely

How does this apply to me?

This study should drive home how important it is to take care of your mouth. Remember, it’s not just about brushing your teeth at least twice a day. Flossing helps to sweep away the biofilms bacteria like Strep mutans form. Visiting the dentist can also help get rid of damaging plaque and seal up any cavities that might have developed. Diet and healthy habits are also essential. Eating a diet low in sugar and high in healthy fruits, vegetables and whole grains is great for your teeth. Finally, smoking is one of the worst things you can do for your mouth as well as your heart, lungs and brain. If you’re a smoker, quitting is a quick way to dramatically boost the health of your body overall.