Streptococcus A12 may help fight cavities

Researchers recently discovered a new strain of bacteria in the mouth that might help keep bad bacteria to a minimum—and could lead to a preventative treatment of cavities using oral probiotics.

While developing an efficacious oral health probiotic entails extensive research, Streptococcus A12, a previously unidentified strain of Streptococcus has been identified as a potential candidate species. The findings were recently published in the journal Applied and Environmental Microbiology.

Maintaining a healthy mouth requires a neutral pH, a relatively neutral chemical environment. As the mouth becomes more acidic it is more conducive toward dental cavities and other health issues.

Bad bacteria on the teeth produce acid, which can dissolve the teeth. Researchers grew interested in what specific bacteria and communities allow the environment to elevate the pH.

Two main compounds previously found in research, urea (secreted in the mouth) and arginine (an essential amino acid), are broken down into ammonia, which aids in neutralizing acid. Both adults and children with few or no cavities were better at breaking down arginine than those with cavities. Scientists understand that bacteria are responsible for breaking down urea and arginine, but further research was required to understand how the bacteria break down the compounds and inhibit cavities.

The approach would be similar to probiotics that promote gut health. A probiotic formula could be developed from natural beneficial bacteria in humans who can break down arginine at high capacity. This could potentially prevent oral health diseases by rebalancing the oral microbiome.

A12 is particularly potent in fighting Streptococcus mutans, a species that metabolizes sugar into lactic acid and contributes to acidic conditions in the mouth responsible for causing cavities.

The research also indicated that A12 not only helps neutralize acid, it often destroys Streptococcus mutans.

Researchers noticed that when A12 inhibits Streptococcus mutans normal processes. When grown together, S. mutans does not grow very well or make biofilms, also known as dental plaque.

Dental plaque, a mass of bacteria that grows on a tooth’s surface, can contribute to cavities.

The Oral Microbiome and Cavities

Researchers isolated more than 2,000 bacteria from samples and then screened them to find bacteria to inhibit cavity. Fifty-four of these bacteria metabolized arginine. A12 was the only strain of bacteria that represented all of the properties researchers were looking for to prevent cavities in a probiotic formula.

Researchers believe A12 may be used as a screening tool to assess the risk of developing cavities if it can be confirmed that is positively influences the health of the oral cavity.

Scientists are continuing to study A12 in larger sample pools to observe how prevalent similar bacteria are in the human mouth.

Future research will focus on observing the genomics and ecology of A12 and related bacteria in the mouth to analyze the mechanisms bacteria use to promote oral health.


Huang, X., Palmer, S., Ahn, S. et al. Characterization of a highly arginolytic Streptococcus species that potently antagonizes Streptococcus mutans. Applied and Environmental Microbiology. 2016. 82(7); 1977. doi:10.1128/AEM.03887-15

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