Which of the following statements about C. diphtheria is false –
**Core Concept**
Corynebacterium diphtheriae is a Gram-positive, rod-shaped bacterium that causes diphtheria, a highly infectious disease characterized by the formation of a toxin-producing membrane in the throat. The bacterium's ability to produce diphtheria toxin is mediated by a lysogenic bacteriophage that carries the toxin gene.
**Why the Correct Answer is Right**
Diphtheria toxin is a potent exotoxin that inhibits protein synthesis by cleaving elongation factor 2 (EF2), leading to cell death. The toxin is produced by the bacterium when it is infected with a specific bacteriophage that carries the toxin gene. The toxin is responsible for the majority of the morbidity and mortality associated with diphtheria.
**Why Each Wrong Option is Incorrect**
* **Option A:** This statement is true, as C. diphtheriae is indeed a Gram-positive bacterium.
* **Option B:** This statement is true, as the bacterium produces a toxin that causes the disease.
* **Option C:** This statement is false, as the toxin is not produced by the bacterium itself, but rather by a lysogenic bacteriophage.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that C. diphtheriae is a toxin-producing bacterium, and its toxin is responsible for the majority of the disease's symptoms. This is a key point to remember when diagnosing and treating patients with diphtheria.
**Correct Answer:** C. The toxin is not produced by the bacterium itself.