Differentiation of Cariogenic Streptococci by Fluorescent Antibody

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Abstract
Eight strains of streptococci were isolated from human carious lesions by the fluorescent-antibody (FA) technique. Seven of these strains produced experimental carles in hamsters or rats maintained on a high sucrose diet. The 8th strain was noncariogenic in animals but possessed some antigenic components in common with the cariogenic strains. On the basis of antigen-antibody reactions by micro-precipitin and agar-gel diffusion patterns, the strains were divided into 4 groups; these groups differed with regard to their cariogenic activity in hamsters. Fluorescein-conjugated antisera, prepared against the human strains, showed some cross-reactions which interfered with the efficacy of the Fa technique in differentiating between the related streptococcal groups. To eliminate these cross-reactions, a small amount of related-strain antisera was added to the fluorescein-conjugated antisera to the cariogenic strains. This technique is effective in blocking cross-reactions and should be tried wherever cross-reactions are encountered in the FA technique.