Identification of Streptococcus mutans serotypes in dental plaque by fluorescent antibody techniques.

The presence of Streptococcus mutuns in dental plaque may be related to human dental caries. The cultural identification of this organism in plaque is not likely to be used routinely in a clinical or epidemiological situation. In an effort to develop a simpler diagnostic means of identifying Strep. mutans in plaque, antisera were prepared for the 5 known serotypes of Strep. mutuns. These immune sera were conjugated with fluorescein isothiocyanate, fractionated to obtain the gamma globulin and titrated against their homologous antigens to obtain working titres. These antisera were compared with cultural methods for their ability to detect Strep. mutuns in plaque samples. Nonspecific fluorescent antibody reactions and weak cross-reactions were essentially eliminated by applying eriochrome black as a counterstain, affer plaque and conjugated antiserum had been incubated. The results suggest that the fluorescent antibody is more sensitive than cultural methods in the detection of Strep. mutans in dental plaque.