Common antigens of streptococcal and non-streptococcal oral bacteria: isolation and biochemical characterization of the extracellular protein antigen.

An extracellular soluble common protein (ECP) has been purified from extracellular soluble fractions of exponential phase cultures of Streptococcus sanguis OMZ9, of a representative strain of each of Bratthall's seven serological groups of Streptococcus mutans, and of one strain each of Lactobacillus salivarius and Actinomyces viscosus. The ECP antigens from the different strains were prepared from SDS-dissociated immunoprecipitates by affinity chromatography on an anti-rabbit immunoglobulin column. The identity of such purified ECP antigens was demonstrated by their behaviour in immunodiffusion analysis, in SDS-PAGE, in which an identical molecular weight (60000) was found, and by virtue of their similar amino acid and sugar compositions. This common antigen (ECP) consisted of 90% protein and 10% sugar.