Virulent Bacterium Variant Increases Caries Risk in Children

Dentistry Today
Photo by Jan Lindmark.


Photo by Jan Lindmark.

Children who are at higher risk of caries may have a more virulent variant of Streptococcus mutans whose adhesive function makes it more aggressive and a better survivor in the oral cavity, according to Umeå University in Sweden. These findings may improve how dentists identify these patients and treat their caries.

“Caries is a lifestyle condition often caused by eating and oral hygiene habits that lead to an acidic pH in the mouth. The pH level has a damaging effect on the enamel and further promotes the growth of acid-producing bacteria such as Streptococcus mutans,” said Nicklas Strömberg, professor and head of the Department of Cariology at the university.

This correlation is accurate for approximately 4 out of 5 individuals with small to moderate risk of developing caries. Yet children with particularly virulent strains of S mutans have a high risk of developing caries regardless of diet or oral hygiene. These variant bacteria have unique adhesive proteins called SpaP and Cnm that improve their ability to survive in the mouth by binding with DMBT1, a protein in otherwise antibacterial saliva, increasing caries development.

One in 5 children in Sweden are considered high-risk patients for developing caries, and up to half of these children are conditioned by the highly virulent types of S mutans. These children do not respond to traditional caries prevention or treatment, and lifestyle variables do not predict their risk of caries.

“This new knowledge of the identified types of bacteria and how they initiate caries development could be used to improve individualized dental care. The presence of the bacteria could be used as biomarkers for early detection of high-risk patients. Also, their adhesive function could constitute new targets for treatment,” said Strömberg.

The researchers followed 452 children from the ages of 12 to 17 years during the 5-year study, collecting their saliva and monitoring their dental health. After analysis of saliva samples and isolated bacterial strains, the children were divided into various risk groupings based on what genetic types of caries bacteria they carried. At the 5-year follow-up, the researchers examined how caries had developed in the various risk groupings. 

“In another study yet to be published, we show that other high-risk children have genetic defects in their saliva receptors for bacteria, and the affected genes may involve those in so-called autoimmune diseases,” said Strömberg. “It’s still important to emphasize that caries in many individuals of low to moderate risk is still modulated by eating and oral hygiene habits.”

The study, “Streptococcus Mutans Adhesin Biotypes that Match and Predict Individual Caries Development,” was published by EBio Medicine.

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