Serotyping and subtyping of Neisseria meningitidis isolates by co-agglutination, dot-blotting and ELISA.

Typing of meningococci with a panel of serotype and subtype specific monoclonal antibodies (MAbs) was compared in co-agglutination, dot-blotting and ELISA tests. Twenty reference strains, 50 case isolates and 133 throat isolates from healthy carriers were studied. The typing results with dot-blotting and ELISA were identical, whereas co-agglutination gave different results for three case and 24 carrier strains. The distribution of serotypes and subtypes among the strains is reported. The combination of the subtypes P1.1 and P1.15 in a serotype 15 patient strain was observed. With one case strain and 15 carrier strains, neither serotype nor subtype could be determined. Non-typable and non-subtypable isolates were further characterised by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Co-agglutination is useful for typing small numbers of strains with a few MAbs, but less suitable for large-scale typing than the other two methods. Dot-blotting needs less expensive equipment, smaller volumes of antibodies and fewer manipulations than ELISA.