Diphtheria is caused by which organism?

Diphtheria is caused by which organism?

• A. Corynebacterium diphtheriae
• B. Staphylococcus aureus
• C. Streptococcus pneumoniae
• D. Neisseria gonorrhoeae

Answer: (A)

Diphtheria is caused by Corynebacterium diphtheriae, a Gram-positive, non-spore-forming rod that produces a potent exotoxin. This toxin blocks protein synthesis by ADP-ribosylating elongation factor-2, leading to the characteristic pseudomembrane in the throat and possible systemic effects. The other organisms listed cause different diseases—Staphylococcus aureus typically causes skin infections and toxic syndromes, Streptococcus pneumoniae causes pneumonia and meningitis, and Neisseria gonorrhoeae causes gonorrhea—so they are not responsible for diphtheria.

Diphtheria is caused by Corynebacterium diphtheriae, a Gram-positive, non-spore-forming rod that produces a potent exotoxin. This toxin blocks protein synthesis by ADP-ribosylating elongation factor-2, leading to the characteristic pseudomembrane in the throat and possible systemic effects. The other organisms listed cause different diseases—Staphylococcus aureus typically causes skin infections and toxic syndromes, Streptococcus pneumoniae causes pneumonia and meningitis, and Neisseria gonorrhoeae causes gonorrhea—so they are not responsible for diphtheria.