What is true about Bordetella pertussis –
**Core Concept**
Bordetella pertussis is a gram-negative coccobacillus responsible for causing pertussis, also known as whooping cough. The bacterium produces various virulence factors that contribute to its pathogenicity.
**Why the Correct Answer is Right**
The correct answer is related to the toxin produced by B. pertussis. The toxin responsible for the disease's pathophysiology is the **pertussis toxin (PT)**. Pertussis toxin works by **ADP-ribosylating** the alpha subunit of the G protein, **Gαi**, which leads to the inhibition of **adenylyl cyclase** and a subsequent decrease in **cyclic AMP (cAMP)** levels. This results in a reduction of **inhibitory neurotransmitter** release, leading to increased **parasympathetic tone** and **bronchoconstriction**.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because B. pertussis does not produce a toxin that causes the disease's hallmark symptom of a persistent cough.
* **Option B:** This option is incorrect because while B. pertussis does cause a severe cough, the toxin responsible for this symptom is not the **tracheal cytotoxin**.
* **Option C:** This option is incorrect because B. pertussis is not primarily a cause of **meningitis**.
* **Option D:** This option is incorrect because while B. pertussis is a vaccine-preventable disease, the vaccine does not work by **inactivating** the toxin.
**Clinical Pearl / High-Yield Fact**
Pertussis toxin can cause a decrease in **cAMP** levels, leading to increased **parasympathetic tone** and **bronchoconstriction**. This is a key pathophysiological mechanism underlying the disease's symptoms.
**Correct Answer:** B.