The Unique Antigenic Determinants of the Different Serotypes of Streptococcus

Question

The unique antigenic determinants of the different serotypes of Streptococcus pneumoniae are found
A) on the cell-surface M proteins.
B) on the capsular polysaccharides.
C) in the bacterial cell wall.
D) in the inclusions in the periplasmic space.

Accepted Answer

The unique antigenic determinants of the different serotypes of Streptococcus pneumoniae are found on the capsular polysaccharides, which are distinct for each serotype. This is why vaccination against pneumococcal disease requires a vaccine that targets multiple serotypes. M proteins are found in the cell wall of some strains of Streptococcus pyogenes, but not in Streptococcus pneumoniae. Inclusions in the periplasmic space and the bacterial cell wall are not known to contain the unique antigenic determinants of the different serotypes of Streptococcus pneumoniae.