An alternative approach to typing of Streptococcus pneumoniae strains by coagglutination.

The coagglutination test, which uses staphylococcal protein A for typing strains of Streptococcus pneumoniae was extended to include typing within 13 groups. Typing was performed using the factors remaining in group antisera after absorption with a strain of a type within the group. 93 of 99 strains of S. pneumoniae, which belonged to one of the 13 groups included in the 23 valent vaccine formulation were correctly identified when compared to the capsular reaction test.