The diagnosis of Listeria monocytogenes serogroup 4 infections in humans by the detection of soluble antigen in cerebrospinal fluid by ELISA

With a panel of anti-Listeria monoclonal antibodies, soluble antigen was identified by ELISA in the cerebrospinal fluid samples (CSF) of patients infected by strains of Listeria monocytogenes serogroup 4. Antigen was captured by an anti-Listeria monoclonal antibody (CL2) coated on to microtitre wells, which was detected by the sequential addition of CL2 conjugated to flourescein isothiocyanate (FITC), followed by a peroxidase labelled anti-FITC monoclonal antibody. The test was 100% specific, and antigen was detected in 27% ( 18 67) of patients infected with L. monocytogenes serogroup 4, and in two out of 62 patients where listeriosis was suspected. Antigen was not detected in 270 other CSFs tested. Antigen was only detected in CSFs taken within seven days after onset of illness, where 52% of patients had detectable antigen.