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Setting: Macha, Zambia., Objective: To assess the benefits of auramine-O staining fluorescence microscopy and Mycobacterial Growth Indicator Tube (MGIT) liquid culture with molecular identification in tuberculosis (TB) diagnostics., Design: One hundred patients suspected of TB were subjected to three sputum sample examinations applying Ziehl-Neelsen (ZN) and auramine-O staining and MGIT culture. Positive cultures were identified using the GenoType CM assay; cultures identified as Mycobacterium tuberculosis complex were the gold standard for a diagnosis of TB., Results: The 100 patients produced 271 sputum samples; of these, 30 patients had positive cultures. M. tuberculosis complex bacilli were isolated in 17 (56.7%) patients, non-tuberculous mycobacteria (NTM) in 11 (36.7%) and other acid-fast bacilli in two. Forty-eight samples (17.7%) were contaminated. Auramine-O detected 16 (57.1%) patients culture-positive for mycobacteria and 12 patients with culture-proven TB, vs. respectively 8 (28.6%, P = 0.008) and 7 (41.2%, P = 0.044) for ZN. Three of eight auramine-positive/ZN-negative patients were culture-positive for NTM only., Conclusion: The auramine-O method significantly increases sensitivity, although the higher NTM detection rate implies that this does not in itself lead to a more accurate diagnosis of TB. MGIT culture is highly sensitive, although contamination rates were a drawback; the high frequency of NTM isolation warrants a robust identification method.

Comparisons were made in Lusaka and in London between manual staining and staining in an automatic machine with auramine-phenol of direct smears of sputum and other types of specimen for acid-fast bacilli. No evidence was obtained of carry-over of acid-fast bacilli from positive to negative smears during machine staining. There was improved contrast between bacilli and the background in smears prepared with the machine.