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.

Isolation of tubercle bacilli from sputum samples of patients in the field studies by the cetylpyridinium chloride-sodium chloride & sodium hydroxide methods.

A total of 125 sputum specimens, collected in the field, were homogenised, aliquoted in sterile universal containers and randomly allocated to the cetylpyridinium chloride - sodium chloride (CPC-NaCl) method and sodium hydroxide (NaOH) method for culture of tubercle bacilli. After storage for 8 days at ambient temperature in the field laboratory at Thiruvallur, the aliquots were transported to the main laboratory at Madras where they were processed for culture by the respective methods. The yield of positive cultures in the CPC-NaCl (31/125) method was only marginally better than that in the NaOH method (27/125) (95% CI being-3.4 to 9.8%), while the contamination of cultures was significantly less in the CPC-NaCl method (3/125) than in the NaOH method (12/125) (95% CI being 2.2 to 12.2%). As the CPC-NaCl method has advantages over the NaOH method in reducing contamination, in augmenting the yield of positive cultures and also in its simplicity, it can be applied in field studies.