Restricted distribution of Streptococcus milleri carbohydrate type antigens amongst other viridans streptococci

The distribution of oral Streptococcus milleri carbohydrate type antigens in other viridans streptococcus species was examined. Rantz-Randall extracts of cells of the test strains grown in broth containing glucose were allowed to react with typing or grouping antisera for S. milleri serotypes a-k, or Lancefield groups A-G and K. Of 93 strains comprising more than 12 streptococcal species that included S. mutans and S. sanguis complexes, only 15 S. salivarius strains and one S. mitis strain were immunologically related to S. milleri serotype f. Unlike S. milleri strains, S. salivarius type f strains belonged to Lancefield group K, whereas the S. mitis strain was closely related to S. milleri serotype f but did not react with any of the Lancefield grouping antisera tested. Results suggest that oral S. milleri strains can be distinguished serologically from other oral viridans streptococci and that the typing antisera used in our researches might differentiate S. milleri isolates from the mouth from those associated with systemic purulent infections.