A newer approach for the laboratory diagnosis of tuberculous meningitis.

In this prospective study, a simple method was standardized for measuring circulating mycobacterial antigen in the cerebrospinal fluid (CSF) for the laboratory diagnosis of tuberculous meningitis (TBM). The heat-inactivated CSF specimens from tuberculous and non-tuberculous patients were subjected to sodium dodecyl sulfate (SDS) - polyacrylamide gel electrophoresis (PAGE) (SDS-PAGE) and they were subsequently transferred onto nitrocellulose membrane (NCM) Using a rabbit polyvalent antibody to M tuberculosis, a heat stable 82 kDa mycobacterial antigen was demonstrated in the CSFs of patients with TBM. This antigen was conspicuous by its absence in the CSFs of non-tuberculous subjects. Due to inactivation of CSF specimens, there is a minimal risk of handling of infectious material in the laboratory. Besides, this newer approach is simple, inexpensive and can be readily applied in any routine clinical laboratory and it is particularly suited to developing countries.

Correlation between the isolation of Mycobacterium tuberculosis and estimation of mycobacterial antigen in cisternal, ventricular and lumbar cerebrospinal fluids of patients with tuberculous meningitis.

In the study Mycobacterium tuberculosis was isolated in the cerebrospinal fluid (CSF) specimens of patients with tuberculous meningitis (TBM) by the conventional bacteriological technique. The isolation rate of M. tuberculosis was found to be 11.5% in lumbar, 75% in ventricular and 87.5% in cisternal CSFs. Low isolation rate of M. tuberculosis in lumbar CSF is due the low density of tubercle bacilli in lumbar CSF than in cisternal CSF. However M. tuberculosis antigen 5 is present in significant concentration in CSFs. The antigen concentration in CSF was estimated by an inhibition enzyme-linked immunosorbent assay (ELISA). Since CSF specimens can not be collected from ventricular or cisternal routes for the routine bacteriological investigations in patients with TBM, estimation of M. tuberculosis antigen 5 concentration in lumbar CSF by an inhibition ELISA may be considered as an adjunct in the laboratory diagnosis of TBM. This is particularly relevant in those patients in whom bacteriological methods fail to demonstrate M. tuberculosis in CSF specimens.

Circulating immune complexes in cerebrospinal fluid of patients with tuberculous meningitis.

Circulating immune complexes (ICs) were isolated from cerebrospinal fluids (CSFs) of patients with tuberculous meningitis (TBM), non-tuberculous neurological diseases by a polyethylene glycol (PEG) precipitation method. Mycobacterium tuberculosis antigen 5 was detected in CICs of 30% patients with TBM, by sandwich ELISA. CIC level decreases during antituberculosis chemotherapy and therefore its detection can provide a method to monitor the therapeutic schedule in patients with TBM.

Rapid diagnosis of tuberculous meningitis with a dot enzyme immunoassay to detect antibody in cerebrospinal fluid.

A simple dot enzyme immunoassay (Dot-EIA) was carried out to detect antibody to Mycobacterium tuberculosis antigen 5 in cerebrospinal fluid (CSF) specimens from 40 patients with a clinical diagnosis of tuberculous meningitis (TBM). The assay gave a positive reaction in all ten patients with culture proven TBM. In 30 culture negative patients with TBM, the assay was positive at a titre of 1:16 in 18 patients. In 40 patients with non-tuberculous neurological diseases (control group) the assay was negative at a titre of 1:16. The Dot-EIA had an overall sensitivity of 70% and a specificity of 100% in the diagnosis of TBM. This assay could be used as a rapid screening test to establish the diagnosis of TBM, particularly in patients in whom bacteriological investigations for Mycobacterium tuberculosis in CSF specimens are negative.

Enzyme-linked immunosorbent assay to detect Mycobacterium tuberculosis antigen 5 and antimycobacterial antibody in cerebrospinal fluid of patients with tuberculous meningitis.

Inhibition ELISA and indirect ELISA was standardised to detect Mycobacterium tuberculosis antigen 5 and antimycobacterial antibody in cerebrospinal fluid (CSF) specimens of 75 patients with tuberculous meningitis, (TBM) and 75 patients with non-tuberculous neurological diseases (control group). In both ELISAs, no false-negative results were observed in 15 culture proven patients with TBM. Detection of M. tuberculosis antigen 5 is more sensitive than detection of antimycobacterial antibody. However, both ELISAs showed 100% specificity for tuberculous aetiology in culture-negative patients with TBM. ELISA should be considered as one of the approaches in the laboratory diagnosis of TBM, particularly when standard bacteriological methods are unable to demonstrate M. tuberculosis in CSF specimens of patients with TBM.

Correlation between culture of Mycobacterium tuberculosis and IgG antibody to Mycobacterium tuberculosis antigen-5 in the cerebrospinal fluid of patients with tuberculous meningitis.

A retrospective study was made of the correlation between culture of Mycobacterium tuberculosis and detection of IgG antibody to M. tuberculosis antigen-5 in cerebrospinal fluid (CSF) by means of an enzyme linked immunosorbent assay (ELISA). Mycobacterium tuberculosis was cultured from the CSF in 14 of 70 patients with a clinical diagnosis of tuberculous meningitis (TBM). IgG antibody to M. tuberculosis antigen-5 was demonstrated in significant titres (80-640) in all 14 culture-positive patients. Thus, positive correlation was observed between culture of M. tuberculosis and detection of IgG antibody in the CSF. As a result of this observation, the CSF from 56 culture-negative patients with a clinical diagnosis TBM was specifically investigated for the detection of IgG antibody to M. tuberculosis antigen-5 and the findings were correlated with those of culture-positive patients. The assay was positive in 34 of 56 patients, the antibody titre ranging between 80 and 640. In the CSF of 70 patients with non-tuberculous neurological diseases, the assay was negative at a dilution of 1 in 80. Thus, detection of IgG antibody to M. tuberculosis antigen-5 by indirect ELISA carried 100% specificity and 60.7% sensitivity for a tuberculous aetiology in culture-negative patients with TBM. The results of this study suggest that indirect ELISA for IgG antibody to M. tuberculosis antigen-5 in CSF holds definite promise in diagnosis of TBM, particularly when repeated cultures of CSF are negative for M. tuberculosis.