Metachromatic Granules Stain
The size of Corynebacterium diphtheriae is very variable, essentially rod-shaped but often showing irregular expansion at one end. Cells frequently lie in small clusters at acute angles to each other in V, L or Y shapes. Gram positive but readily decolorized, non-motile, non-capsulate, non-sporing.
Strains are distributed as beans and stained unevenly. With Metachromatic Granules Stain, deeply stained granules known as metachromatic granules, are found on one side or both sides of diphtheriae.
1. Solution A ( Toluidine Blue )
2. Solution B ( Potassium iodide )