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.