Teichoic Acids of Group

The group antigen of Group D streptococci is a glucose-substituted polymer of a-glycerophosphate (1, 2). In streptococcal extracts it is found in two forms, one, lipid-bound (lipoteichoic acid), the other, lipid-free (3). The two forms are often found together but in differing relative proportions depending on the source of the material and method of extraction. In phenol extracts from washed cocci, the lipoteichoic acid predominates. It is probably released by phenol from association with the streptococcal cell membrane and carries with it a small fragment of the membrane lipid (4). In hydrochloric acid or trichloracetic acid extracts of streptococci and in culture supernatant fluids, the lipid-free form predominates. Both forms of teichoic acid react with Group D antiserum. In our experience, phenol extracts from all Group D strains tested, including representatives of the sub-groups Streptococcus faecalis, Streptococcus faecium, Streptococcus suis, and Streptococcus bovis, give group-specific precipitation reactions. HC1 is less effective than phenol in extracting the lipoteichoic acid. The conventional method for extracting streptococcal group antigens by heating in HC1 at 100°C and pH2 yields, from S. faecalis, sufficient free teichoic acid to precipitate with potent Group D antisera, but from S. suis such extracts may give weak or equivocal reactions (5). In an attempt to account for this difference between S. faecalis and S. suis, we describe here our examination of teichoic acid preparations from a variety of Group D streptococci, including representatives of these two subgroups.