A 5-year-old child presents with a grey pharyngeal membrane that bleeds on removal. Throat swab smears stained with Albert stain show club-shaped bacilli with bluish-black granules at one pole against a green cytoplasm. The polar granules demonstrated here are composed chiefly of:
- A Polymetaphosphate (volutin) ✓
- B Lipid inclusions of mycolic acid
- C Glycogen storage granules
- D Polyhydroxybutyrate
Correct answer: A. Polymetaphosphate (volutin)
Explanation
Albert stain demonstrates metachromatic granules of Corynebacterium diphtheriae. These granules are polymetaphosphate (volutin), which stains bluish-black with toluidine blue while the cytoplasm takes up malachite green. Mycolic acid relates to acid fastness of mycobacteria, not corynebacteria, and polyhydroxybutyrate is a carbon reserve seen in Bacillus species.
Reference: Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.