Antigens and surface components associated with virulence of Actinomyces viscosus

We have isolated a specific cell wall antigen of high molecular weight which appears to be unique to virulent strains of A viscosus and A naeslundii. The antigen is composed of two parts: a polysaccharide moiety containing 6-DOT as the major sugar and determinant of serologic specificity, and a small peptide bearing some resemblance to the peptidoglycan. Other data indicate a positive correlation between the presence of this antigen and an extrachromosomal piece of DNA having most of the properties of a bacterial plasmid. The specific function of the 6-DOT antigen in disease production is not known, but its clear association with virulent strains suggests the possibility of monitoring specific populations of oral actinomycetes.