A throat swab smear from a child with membranous pharyngitis is stained by Albert stain. The expected finding that supports the diagnosis of Corynebacterium diphtheriae is:
- A Blue cocci in chains surrounded by a clear halo
- B Purple rods arranged in Chinese letter patterns with pink terminal spores
- C Green rods containing bluish-black metachromatic granules at the poles ✓
- D Red branching filaments with beaded acid-fast staining
Correct answer: C. Green rods containing bluish-black metachromatic granules at the poles
Explanation
Albert stain demonstrates the Babes-Ernst granules of Corynebacterium diphtheriae: polymetaphosphate (volutin) granules that stain bluish-black at the poles of the bacillus while the body of the organism stains green. These metachromatic granules are characteristic of corynebacteria and aid presumptive identification before culture on Loeffler serum slope or potassium tellurite medium. Corynebacteria do not form spores, ruling out any description involving terminal spores.
Reference: Paniker's Textbook of Medical Parasitology and Microbiology... Ananthanarayan and Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.