Grouping and cross-reacting antigens of oral lactic acid bacteria.

The grouping antigens from five of the seven serological groups of lactobacilli have been defined with respect to the carbohydrate units responsible for serological specificity. When the antigens are polysaccharides, specificity is more absolute than with the teichoic acids where cross-reactions may occur because of the same or similar carbohydrate substituents, or more particularly because of the common "backbone" structure of the glycerol teichoic acids. This glycerol phosphate "backbone" accounts for a number of reports on the presence of a "common antigen" in gram-positive organisms and their culture fluids, with the amount of extracellular material being particularly high for S mutans strains.