Latex agglutination, counterimmunoelectrophoresis, and protein A co-agglutination in diagnosis of bacterial meningitis.

Specimens of cerebrospinal fluid from 201 patients with meningitis caused by Neisseria meningitidis groups A/B/C/135, Streptococcus pneumoniae (23 types), and Haemophilus influenzae type b were tested for the presence of specific bacterial antigens by latex agglutination, counterimmunoelectrophoresis (CIE), and protein A co-agglutination. Specific antigens were found in 75% of the specimens by latex agglutination and CIE, and in 60% of the specimens by protein A co-agglutination. Non-specific reactions in protein A co-agglutination were prevented by heating the specimens to 100 degrees C for a few minutes. The three methods are simple and quick to perform. The smallest amount of antiserum was used in protein A co-agglutination, but we found this method less sensitive. Latex agglutination and CIE proved to be equally sensitive, but the first method was easier to adopt in practice.