Evaluation of a PCR-immunoassay technique for detection of Neisseria meningitidis in cerebrospinal fluid and peripheral blood

A multiplex PCR-immunoassay for the rapid diagnosis of bacterial meningitis from cerebrospinal fluid (CSF) or peripheral blood was compared with conve ntional microbiological techniques used in the routine diagnostic laborator y The multiplex PCR was designed to detect simultaneously a universal conse rved sequence coding for bacterial 16S rRNA and the Neisseria meningitidis porA gene. The PCR-immunoassay had a detection limit of (3-5) x 10(2) cfu/m l (equivalent to 1-3 cfu/PCR) with spiked CSF or blood samples, compared wi th (3-5)x 10(3) cfu/ml for PCR followed by conventional agarose gel electro phoresis for detection of PCR products, Of 294 CSF samples from patients su spected on clinical grounds of suffering from meningitis, the PCR-immunoass ay detected bacterial DNA in 29 CSF samples, 15 of which were also positive for N, meningitidis DNA, The 29 positive CSF samples comprised 25 samples that were also reported positive and four that were reported negative by co nventional methodology; the latter four were all positive for N, meningitid is by the PCR-immunoassay Of 173 peripheral blood samples examined, the PCR -immunoassay detected bacterial DNA in 18 samples, 14 of which were also po sitive for N, meningitidis DNA, In comparison, only 10 samples were reporte d positive for N, meningitidis by conventional methodology, All negative PC R-immunoassay results correlated with those obtained by conventional method ology for both CSF and blood samples. The sensitivity and speed of the PCR- immunoassay system indicated that it could be used as a routine diagnostic test for meningococcal meningitis, enabling a diagnosis to be made within 4 h of receipt of the specimen.