Practical considerations in using counterimmunoelectrophoresis to identify the principal causative agents of bacterial meningitis.

Many clinical laboratories are currently using counterimmunoelectrophoresis (CIE) as an aid in the rapid diagnosis of bacterial meningitis. Because cross-reactions among causative agents have been reported, the present study was undertaken to explore the problems that might occur when reference and commercial antisera are used in CIE. Broth cultures of 35 bacterial strains were tested with 76 reference and commercial antisera by CIE. Some of the antisera tested failed to react with their homologous strains. Furthermore, several cross-reactions between genera, as well as within species, were noted. These findings suggest that precautions must be taken to insure that all materials used in CIE tests are of high quality. If properly performed and interpreted, CIE may be a valuable adjunct in the identification of organisms causing bacterial meningitis, but it is, nevertheless, a presumptive test and should not be used to replace the Gram stain and culture techniques.