Which of the following bacteria act by increasing cAMP
**Core Concept**
The question is testing the student's knowledge of bacterial adenylyl cyclase toxins, which increase intracellular cyclic adenosine monophosphate (cAMP) levels, leading to various cellular effects. These toxins are produced by certain pathogens and play a crucial role in their pathogenicity.
**Why the Correct Answer is Right**
The correct answer is likely Vibrio cholerae, which produces the cholera toxin (CT). Cholera toxin is an exotoxin that activates the adenylyl cyclase enzyme in intestinal epithelial cells, leading to a significant increase in intracellular cAMP levels. This increase in cAMP triggers a cascade of events that result in the secretion of chloride ions into the intestinal lumen, causing severe diarrhea and dehydration.
**Why Each Wrong Option is Incorrect**
* **Option A:** Bordetella pertussis produces pertussis toxin, which inhibits Gi proteins, thereby increasing cAMP levels indirectly. However, it is not the correct answer because the question asks for a bacterium that acts by directly increasing cAMP.
* **Option B:** Escherichia coli produces various virulence factors, but it is not directly associated with increasing cAMP levels.
* **Option D:** Shigella dysenteriae produces Shiga toxin, which inhibits protein synthesis and causes cell death, but it is not related to increasing cAMP levels.
**Clinical Pearl / High-Yield Fact**
The cholera toxin's mechanism of increasing cAMP levels is a classic example of a bacterial pathogen exploiting the host cell's signaling pathways to cause disease. This knowledge is essential for understanding the pathogenesis of cholera and developing effective treatments.
**Correct Answer:** C. Vibrio cholerae