A 5-year-old unvaccinated child presents with fever, sore throat, and a dirty-grey adherent membrane over both tonsils. Removal of the membrane leaves a bleeding raw surface. Cervical nodes are enlarged giving a bull-neck appearance. The organism responsible produces disease by means of:
- A M protein-mediated resistance to phagocytosis
- B An exotoxin that inhibits protein synthesis by ADP-ribosylation of EF-2 ✓
- C Diphthamide-independent invasion of epithelial cells
- D Shiga-like toxin causing capillary thrombosis
Correct answer: B. An exotoxin that inhibits protein synthesis by ADP-ribosylation of EF-2
Explanation
Corynebacterium diphtheriae elaborates a potent exotoxin that ADP-ribosylates elongation factor 2, halting protein synthesis and producing local necrosis, the adherent pseudomembrane that bleeds when removed, and distant myocardial and neural toxicity. M protein is the virulence factor of group B streptococcus, the main differential for exudative tonsillitis, but streptococcal exudate is not an adherent membrane and leaves no bleeding surface on removal.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.