A novel method of staining acid-fast bacilli in sputum containers.

Background & Objectives: Making centrifuged deposit smears from sputum to detect acid-fast bacilli (AFB) is considered hazardous. We carried out this study to stain the centrifuged deposits with carbol-fuchsin in sputum containers and to decolourize and counterstain their smears made on glass slides.

Methods: The centrifuged deposits of 180 sputum samples from pulmonary tuberculosis patients were used for making smears (initial deposit smears) and staining by Ziehl-Neelsen (ZN) method for the detection of AFB. Each of the sputum deposit was then treated with one ml of 1 per cent carbol-fuchsin and a smear made between 2 to 3 h was then decolourized and counterstained by the same procedures followed in ZN method (2 h stained deposit smear). The coded initial deposit smears and the corresponding 2 h stained deposit smears were read by the same readers and the results compared.

Results: One hundred and fifty (70 positive and 80 negative) 2 h stained deposit smears were compared with initial deposit smears and the difference was not statistically significant.

Interpretation & Conclusion: Centrifuged deposits of sputum in sputum containers can be stained by carbol-fuchsin within 2-3 h and their smears made subsequently on glass slides can then be decolourized and counterstained by the procedures followed in ZN method for detection of AFB by light microscopy.