Determination of bacterial meningitis: a retrospective study of 80 cerebrospinal fluid specimens evaluated by four in vitro methods.

A total of 80 cerebrospinal fluid specimens were analyzed for bacterial meningitis by four procedures readily available to most laboratories. These tests included routine culturing. Gram staining, countercurrent immunoelectrophoresis, staphylococcal coagglutination (CoA) with laboratory-prepared reagents, and CoA with Pharmacia Diagnostics reagents. A total of 56 specimens were positive for bacterial agents by routine culturing: Gram stain results were positive for 64% of all specimens positive by culturing. For 36 specimens from patients with suspected meningitis due to either Haemophilus influenzae type b, Streptococcus pneumoniae, or group B streptococci, detection was 97% with Pharmacia CoA reagents, 94% with laboratory-prepared CoA reagents, 89% with routine culturing, 78% with countercurrent immunoelectrophoresis, and 75% with Gram staining. One specimen which contained Klebsiella pneumoniae was false positive for S. pneumoniae in tests with both of the CoA reagents and in countercurrent immunoelectrophoresis. A Gram stain of this specimen clearly showed gram-negative bacilli, which were confirmed by culturing. Although a positive culture and a positive Gram stain are definitive evidence of bacterial meningitis, rapid immunological tests can provide valuable clinical information as an adjunct to culture and Gram stain results. Serological tests with Pharmacia CoA reagents produced more positive results than either laboratory-prepared CoA reagents or countercurrent immunoelectrophoresis.