A 4-year-old unvaccinated child presents with bilateral conjunctival congestion, purulent conjunctivitis, and pharyngitis. Giemsa staining of a conjunctival scraping shows intracytoplasmic basophilic inclusions. Which Gram-positive organism with a similar toxin-mediated pathogenesis is the most important differential in the context of vaccine-preventable respiratory infections?

• A Streptococcus pneumoniae
• B Corynebacterium diphtheriae ✓
• C Bordetella pertussis
• D Haemophilus influenzae type b

Explanation

The vignette describes trachoma caused by Chlamydia trachomatis (intracytoplasmic inclusions), but among the Gram-positive vaccine-preventable options, Corynebacterium diphtheriae is the only Gram-positive organism listed. Both C. diphtheriae and C. trachomatis share the feature of being vaccine-preventable or causing preventable disease, and diphtheria toxin is a classic example of toxin-mediated disease from a Gram-positive organism. C. diphtheriae is Gram-positive; B. pertussis and H. influenzae are Gram-negative. S. pneumoniae is Gram-positive but not toxin-mediated in the classic diphtheria sense.

Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.