Purification and characterization of a rhamnose-containing cell wall antigen of Streptococcus mutans B13 (serotype d)

Abstract

A rhamnose-containing polysaccharide (RCP) was extracted and purified from cell walls of Streptococcus mutans B13 (serotype d) and was chemically and immunologically characterized. Walls were initially extracted with 5% trichloroacetic acid at 4 degrees C to remove the serotype antigen and were then sequentially extracted with increasing concentrations of hot acid. Extracts lacking galactose were combined and chromatographed on a column of diethylaminoethyl--Sephadex A25. The purified RCP contained 90% carbohydrate, 1.4% protein, and 0.16% phosphorus. Analysis by gas chromatography indicated that the RCP was composed of rhamnose and glucose in a 1.6:1 ratio. RCP was immunogenic in rabbits when animals were immunized with whole cells or cell walls. Antisera prepared against partially extracted cell walls of B13 appeared specific for RCP. These sera were not reactive with purified serotype d antigen or lipoteichoic acid in passive hemagglutination assays or by agar gel diffusion. The RCP appeared to be a cell wall polysaccharide that was both chemically and immunologically distinct from the serotype d antigen.