Typing of pneumococci by using 12 pooled antisera

A new simplified chessboard system for typing of Streptococcus pneumoniae is described. It is intended for typing or grouping of 90 to 95% of the pneumococcal strains most commonly isolated from blood or cerebrospinal fluid and is based on 12 pooled diagnostic antisera, each reacting with 7 to 11 single types, together covering the 23 different vaccine-related types as well as 25 other cross-reacting types. Worldwide surveillance of the type distribution is important in order to ensure an optimal formulation of pneumococcal polysaccharide vaccines and, in the future, of polysaccharide-protein conjugate vaccines. The simplified typing system described in this paper makes it easier to carry out surveillance in other than specialized reference laboratories. Finally, it takes advantage of the fact that some types cause disease more often in children--as opposed to adults--than do others.