Biology, immunology, and cariogenicity of Streptococcus mutans

Abstract

It is likely that S. mutans is the primary cariogenic bacterium in both humans and animals. Other bacteria found in actively progressive carious lesions are considered to be secondary invaders, probably commensal with S. mutans with regard to their physiological activities. Only a limited number of species of bacteria other than S. mutans are occasionally found to be cariogenic in experimental animals. Virulence factors of S. mutans responsible for its cariogenicity include the ability to adhere to smooth surfaces and acidogenic-aciduric properties. Adherence to smooth tooth surfaces is responsible for cariogenic plaque formation by S. mutans and is mediated by the de novo synthesis of a glucose polymer from dietary sucrose. The synthesis is due to the action of cell-free or cell-associated forms of GTases. This explains the marked caries-inducing property of sucrose in diets. In terms of bacterial taxonomy, the species S. mutans includes a number of heterogeneous strains. Various immunological, biological, and biochemical properties and the epidemiological distribution of S. mutans have been discussed in this review with special reference to the seven serotypes of the microorganism. The occurrence of S. mutans in subacute endocarditis and the possibilities of a vaccine against dental caries have also been discussed.