Serological Methods for Rapid Diagnosis of Haemophilus Influenzae, Neisseria Meningitidis and Streptococcus Pneumoniae in Cerebrospinal Fluid: A Comparison of Co-agglutination, Immunofluorescence and Immunoelectroosmophoresis

Abstract

Three serological techniques, co-agglutination (COA), immunofluorescence (IFL) and immunoelectroosmophoresis (IEOP) were used for the detection of Haemophilus influenzae (Hi), Neisseria meningitidis (MC) and Streptococcus pneumoniae (PNC) in cerebrospinal fluid (CSF) from 75 patients with meningitis caused by these bacteria. The yields obtained with the serological methods were compared to each other, conventional culture and direct microscopy (Dm). The COA technique (53.3 % positive) was shown to be as sensitive as IEOP (54.7 % positive). IFL was positive in 84 % of the CSF specimens. Culture was found to be the most sensitive method (92 % positive) and a presumptive diagnosis was arrived at by Dm in 74.7 % of the specimens. The specificity of the serological methods was excellent. Their sensitivity levels were correlated to the quantity of bacteria in CSF specimens as measured by the number of colony forming units (CFU) per ml. Both COA and IEOP were regularly negative in concentrations below 10⁴ to 10⁵ CFU/ml while IFL and Dm detected bacteria as low as 8×10¹ CFU/ml. In experimental tests with purified meningococcal polysaccharides the COA method detected 8 ng/ml of serogroup A antigen and 12 ng/ml of serogroup C antigen. The corresponding levels for detection with IEOP were 31 ng/ml (serogroup A) and 12 ng/ml. Each of the 3 rapid serological tests was found to be a valuable adjunct to conventional Dm and culture. The advantages of the COA technique compared to IFL and IEOP are that it is more rapid, less laborious and is performed without technical equipment.