False about diphtheria is
**Core Concept**
Diphtheria is a bacterial infection caused by Corynebacterium diphtheriae, characterized by the formation of a pseudomembrane in the throat, leading to respiratory obstruction and potentially life-threatening complications. The toxin produced by the bacteria is responsible for the majority of the disease's symptoms.
**Why the Correct Answer is Right**
The toxin, diphtheria toxin, is produced by the bacteria and acts by inhibiting protein synthesis in host cells. It does this by catalyzing the transfer of an adenosine diphosphate (ADP)-ribosyl group to elongation factor 2 (EF-2), a critical factor in the initiation of protein synthesis. This inhibition of protein synthesis leads to the characteristic symptoms of diphtheria, including respiratory failure and cardiac complications.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because diphtheria toxin is indeed produced by Corynebacterium diphtheriae.
**Option B:** Incorrect because the toxin does not act by inhibiting the cell membrane's permeability.
**Option C:** Incorrect because while diphtheria toxin does affect protein synthesis, it does not act by inhibiting the initiation of transcription.
**Clinical Pearl / High-Yield Fact**
Diphtheria toxin is a classic example of a ribotoxin, a type of toxin that specifically targets the ribosome and inhibits protein synthesis. This mechanism of action is unique among bacterial toxins and is responsible for the toxin's high degree of specificity and potency.
**Correct Answer: D.**