It demonstrates the presence of metachromatic granules found in Corynebacterium diphtheriae. Smears of throat swab are useful in the diagnosis of diphtheria by Albert’s staining method.

Reagents

1. Albert’s solution ‘A’

a) Add 1.0 ml of glacial acetic acid to 99 ml of distilled water.

b) Add 0.15 g of toluidine blue and 0.2 g of malachite green in 2.0 ml of (95%) ethyl alcohol by grinding in a mortar.

c) Mix solution (a) and solution (b). Keep for 24 hours and afterwards filter it and store in an amber colored dropping bottle.

2. Albert’s solution ‘B’

a) Add 3.0 g of potassium iodide in 100 ml of distilled water.

b) Add 2.0 g of iodine in solution (a). Mix thoroughly and store in an amber colored dropping bottle.

Stability of the Reagents

The reagents are stable at room temperature (25°C ± 5°C).

Procedure

1. Flood the heat fixed smear with Albert’s staining solution ‘A’ for 5 minutes.

2. Drain the staining solution but do not wash.

3. Flood with solution ‘B’ and keep for 1 to 2 minutes.

4. Wash carefully under running tap water, drain, blot dry and examine under oil immersion objective.

Results

1. Metachromatic granules: Bluish black.

2. Bacillary body: Green or bluish green.