Isolation of Mycobacterium tuberculosis from cerebrospinal fluid by the centrifugation & filtration methods

Cerebrospinal fluid (CSF) samples were collected in 2 bottles each, from 112 children, examined clinically for tuberculous meningitis (TBM). One was processed by the centrifugation method and the other by the filtration method for the isolation of M. tuberculosis. Of these specimens, 11 and 13 yielded M. tuberculosis by the centrifugation method and the filtration method, respectively. In 7 specimens M. tuberculosis was isolated by both the methods; in 4, only by the centrifugation method, and in 6, only by the filtration method. Using both the methods, 17 (15.2%) of 112 specimens were culture positive for M. tuberculosis. The improvement in the rate of isolation, thus obtained, assumes importance as the confirmation of the diagnosis of TBM in all the clinically suspected cases is always desired. Moreover, the filtration method is simple and inexpensive and it can be carried out even in remote hospitals and the membranes, after filtration, can be transported to central mycobacteriology laboratory for culture of tubercle bacilli.