Performing Acid-Fast Bacillus (AFB) Staining

Introduction

Acid-Fast Bacillus (AFB) staining is a crucial laboratory technique used to detect Mycobacterium species, particularly Mycobacterium tuberculosis. This staining method differentiates acid-fast bacteria from non-acid-fast bacteria using specialized reagents.

Materials Required

• Carbol fuchsin dye
• Acid-alcohol (decolorizer)
• Methylene blue or malachite green (counterstain)
• Glass slides
• Microscope

Step-by-Step Procedure

1. Preparing the Sample

Ensure the bacterial smear is heat-fixed onto the slide before staining.

2. Primary Staining

Flood the smear with carbol fuchsin and heat for several minutes to penetrate the bacterial cell walls.

3. Decolorization

Wash the slide with acid-alcohol to remove excess dye from non-acid-fast organisms.

4. Counterstaining

Apply methylene blue or malachite green to differentiate non-acid-fast bacteria.

5. Microscopic Examination

Examine the stained sample under a microscope. Acid-fast bacteria appear red, while non-acid-fast bacteria appear blue or green.

Clinical Significance

AFB staining aids in the rapid identification of tuberculosis and related diseases, ensuring prompt diagnosis and treatment.