Question

A positive culture of sputum was stained. Carbolfuchsin was added, washed, decolorized, and malachite blue was used as a counterstain. Two entire fields were scanned, and no acid-fast bacilli were found. The most probable cause is:

A. Wrong primary stain was used
B. Wrong counterstain was used
C. Inadequate scanning of the slide
D. Inadequate decolorization

Answer 1

The most probable cause for not finding acid-fast bacilli in the stained culture of sputum is inadequate decolorization.

Step-by-step explanation:

The most probable cause for not finding acid-fast bacilli in the stained culture of sputum is D. Inadequate decolorization. In the acid-fast staining technique, the decolorization step is crucial for distinguishing acid-fast bacteria from other cell types. Acid-fast bacteria resist decolorization due to the presence of mycolic acid in their cell wall, while all other cell types will be decolorized. If the decolorization step is inadequate, acid-fast bacteria may not be clearly visible in the stained sample. The wrong primary or counterstain or inadequate scanning of the slide would not directly affect the appearance of acid-fast bacteria.