Structure elucidation of capsular polysaccharides from Streptococcus pneumoniae serotype 33C, 33D, and revised structure of serotype 33B

- Serotype 33B and 33D have nearly identical repeat units with a one residue difference.
- Serotype 33C is structurally more similar to the 33B/33D than to the 33A/F repeat units.
- Unlike other serogroup 33 polysaccharides, there is no Glcp residue in the 33C repeat unit.
- Serotype 33C has a unique O-acetylation not found in other serogroup 33 polysaccharides.