Albert staining of growth from Loeffler serum slope in a suspected case of pharyngeal diphtheria reveals dark blue bacilli containing bluish-black granules at both poles. These granules are composed of:
- A Lipid droplets rich in mycolic acid
- B Metachromatic volutin granules of polymetaphosphate ✓
- C Glycogen storage bodies formed under anaerobic conditions
- D Aggregates of diphtheria toxin awaiting secretion
Correct answer: B. Metachromatic volutin granules of polymetaphosphate
Explanation
The polar Babes-Ernst granules of Corynebacterium diphtheriae are metachromatic volutin granules made of polymetaphosphate, giving the characteristic club-shaped barred appearance on Albert stain and aiding presumptive identification. They are nutrient storage structures, not lipid (which characterises mycobacteria) and not stored toxin, since diphtheria toxin is secreted extracellularly.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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