Identification of the common antigenic determinant shared by Streptococcus pneumoniae serotypes 33A, 35A, and 20 capsular polysaccharides

- Serotype 33A polysaccharide has the same backbone structure as serotype 33F.
- Serotype 33A has two additional sites of O-acetylation compared to 33F.
- The 33A/33F backbone with one common O-acetylation is proposed epitope for typing serum 33b.
- A 5,6-di-O-acetylated →3)-β-d-Galf5,6Ac-(1→3)-β-d-Glcp-(1→ disaccharide is proposed epitope for typing serum 20b.