Serotype 15C Streptococcus pneumoniae resistant to classical complement deposition and agglutination by polyclonal rabbit anti-capsular 15B sera.

Background: S. pneumoniae (SP) serotypes 15B and 15C are frequent causative agents of invasive pneumococcal disease (IPD), otitis media, and nasopharyngeal colonization in the post PCV13 era. The principal difference between serotypes 15B and 15C is the presence of an O-acetyl group on the pentasaccharide repeating unit of 15B polysaccharide.