Albert stain is a differential staining technique used primarily in microbiology to identify Corynebacterium diphtheriae and, more specifically, to highlight metachromatic granules within the bacteria. These granules are also called volutin granules.
Key Features of Albert Stain:
- Differential Stain: Albert stain differentiates between the cytoplasm and the metachromatic granules within the bacterial cell.
- Target Organism: It's particularly useful for identifying Corynebacterium diphtheriae, the causative agent of diphtheria.
- Metachromatic Granules: These granules store polymerized metaphosphate, and their presence and appearance are key indicators. They stain a different color (purple-black) than the rest of the cell (light green) due to their chemical composition and staining properties.
- Mechanism: The stain contains dyes that have a differential affinity for the cytoplasm and the granules. Albert's stain typically involves two solutions: Albert's stain itself and a mordant that helps fix the stain.
Visual Appearance:
When viewed under a microscope after Albert staining:
- Metachromatic Granules: Appear purple-black.
- Cytoplasm: Appears light green.
Purpose:
The main purpose of Albert stain is:
- Identification of C. diphtheriae: The presence of characteristically stained metachromatic granules aids in the rapid presumptive identification of Corynebacterium diphtheriae in clinical specimens.
- Diagnosis of Diphtheria: It helps in the preliminary diagnosis of diphtheria, although further confirmatory tests are needed.
