A strain of Corynebacterium diphtheriae shows dark-staining metachromatic granules at the poles when stained with Albert stain. The granules are composed primarily of:
- A Poly-beta-hydroxybutyrate
- B Polymetaphosphate ✓
- C Glycogen
- D Polyglutamate
Correct answer: B. Polymetaphosphate
Explanation
Metachromatic granules, also called Babes-Ernst granules or volutin, are storage depots of polymetaphosphate. They stain bluish-black with Albert stain against the greenish-blue bacillary body, giving the characteristic Chinese letter arrangement clue in diphtheria. Poly-beta-hydroxybutyrate is another storage inclusion but does not account for metachromasia.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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