Purification and immunochemical studies of type b carbohydrate antigen of oral Streptococcus milleri.

The type-specific antigen of serotype b Streptococcus milleri was extracted with trichloroacetic acid from a purified cell wall preparation of the strain NCTC 10708 and then purified on a DEAE-Sephadex A-25 column, followed by a Sephadex G-100 column. The antigen was composed of rhamnose and glucose in a molar ratio of 1.7:1.0, with a trace of galactosamine (0.1). The quantitative precipitin inhibition test with various haptenic sugars showed that rhamnose gave the greatest inhibition, whereas glucose and its related carbohydrates were less effective. The major carbohydrate components of the Rantz-Randall extracts from cells of all four serotype b strains tested were also rhamnose and glucose. These results suggest that rhamnose is structurally involved in the immunodeterminant of the serotype b-specific antigen of oral S. milleri.