Adherence inhibition of Streptococcus mutans: an assay reflecting a possible role of antibody in dental caries prophylaxis.

Adherence of cariogenic streptococci to the smooth surfaces of teeth has been shown to lead to plaque formation and ultimately to caries production. This adherence can be reproduced in vitro and requires sucrose in the growth media. The work reported here describes the development of an assay based on the ability of immune rabbit serum to inhibit adherence of Streptococcus mutans 6715 to glass surfaces. Rabbits were immunized with Formalin-killed whole bacteria. Sera were titered for adherence inhibition and bacterial agglutination. The former assay was found to be dependent upon immunoglobulin G (IgG) antibody, whereas the latter detected either IgG or IgM antibodies. These two assays appeared to detect different antigens. It was hypothesized that the adherence inhibition assay detects antibody directed against an enzyme, perhaps dextransucrase, responsible for dextran synthesis, since immune serum was found to inhibit incorporation of radiolabel from (14)C-sucrose into cell wall extract. The adherence inhibition assay has potential application for study of other cariogenic bacteria. Studies are being pursued in the hope that this assay may lead to a means of control of dental caries.