Enzyme immunoassay for detection of pneumococcal antigen in cerebrospinal fluid

A solid-phase immunoassay utilizing horse antiserum against the C polysaccharide of Streptococcus pneumoniae and biotinylated rabbit antibodies to type-specific pneumococcal polysaccharides was developed to detect pneumococcal antigens in human body fluids and in broth cultures. Pneumococcal antigen could be detected in broth cultures of serotypes of S. pneumoniae containing as little as 10(2) to 10(3) organisms per ml. The assay system detected pneumococcal antigen in all 25 cerebrospinal fluid specimens obtained from patients with documented pneumococcal meningitis. There were no positive reactions noted in specimens from patients infected with Neisseria meningitidis group A or from patients without evidence of bacterial infection. The solid-phase enzyme immunoassay utilizing these reagents is a sensitive and specific assay for the immunodetection of a wide range of pneumococcal antigens.