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Study identifies new bacterial species involved in dental caries formation

A large study in children has demonstrated a highly complex microbial interaction in dental plaque. (Image: Evgeniy Kalinovskiy/Shutterstock)

PHILADELPHIA, US: It was previously believed that Streptococcus mutans was the main microorganism responsible for dental caries. However, in a recent study, researchers have discovered that another bacterial species, Selenomonas sputigena, plays a major role in dental caries development. The unique insights gained in the study could help in the development of new strategies for caries prevention.

In the study, the researchers analysed samples of plaque from the teeth of 300 children aged 3 to 5 years, half of whom had caries. They then validated their findings on a further set of 116 plaque samples from 3- to 5-year-olds. They found that, although S. sputigena does not cause caries on its own, S. sputigena interacts with S. mutans in a manner that enhances its cariogenic power.

“This was an unexpected finding that gives us new insights into the development of caries, highlights potential future targets for cavity prevention, and reveals novel mechanisms of bacterial biofilm formation that may be relevant in other clinical contexts,” said senior author Prof. Hyun Michel Koo, a founding director of the Center for Innovation and Precision Dentistry at the University of Pennsylvania School of Dental Medicine.

Research has discovered that Selenomonas sputigena interacts with Streptococcus mutans in caries formation. (Image: © 2023 Cho et al., licensed under CC BY 4.0)

The researchers explained that S. mutans metabolises sugars to produce glucans to protect the biofilm bacteria and that S. sputigena can become trapped in the glucans. Once this occurs, S. sputigena grows rapidly, forming honeycomb-shaped superstructures that further encapsulate and protect S. mutans, thus increasing acid production within the plaque.

The study was a collaboration between the University of Pennsylvania School of Dental Medicine and the University of North Carolina at Chapel Hill Adams School of Dentistry and Gillings School of Global Public Health. “This was a perfect example of collaborative science that couldn’t have been done without the complementary expertise of many groups and individual investigators and trainees,” said co-author Prof. Kimon Divaris from the University of North Carolina at Chapel Hill.

The researchers are now planning to further investigate how S. sputigena ends up in the aerobic environment of the tooth surface. “This phenomenon in which a bacterium from one type of environment moves into a new environment and interacts with the bacteria living there, building these remarkable superstructures, should be of broad interest to microbiologists,” Prof. Koo concluded.

The study, titled “Selenomonas sputigena acts as a pathobiont mediating spatial structure and biofilm virulence in early childhood caries”, was published online on 22 May 2023 in Nature Communications.

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