Rapid detection of bacteria in cerebrospinal fluid by immunofluorescence staining on membrane filters

A filter-fluorescent-antibody (FFA) staining procedure was developed for detection of bacteria in cerebrospinal fluid (CSF). The sensitivity of this procedure was determined and compared with that of the slide Gram stain of centrifuged samples, latex agglutination, and a previously developed filter Gram stain. Serial 10-fold dilutions of filter-sterilized CSF seeded with logarithmic-phase organisms were examined by each method and cultured to determine colony-forming bacteria. The bacteria included Haemophilus influenzae type b; Neisseria meningitidis group B, C, and W135; Streptococcus pneumoniae types 6A and 23F; and group B Streptococcus species. FFA was found to be equal in sensitivity to the filter Gram stain (P greater than 0.30). Both filter-staining procedures had greater sensitivity than the slide Gram stain of centrifuged sediment (P less than 0.02) and latex agglutination (P less than 0.0001). Addition of human leukocytes at a concentration of 5 to 10 cells per oil immersion field did not decrease sensitivity of the FFA procedure, although background fluorescence increased. FFA is a rapid and dependable procedure for detection of low numbers of bacteria in CSF. Evaluation of FFA with clinical specimens is needed.