**Core Concept**
Pseudomembranous colitis, also known as Clostridioides difficile (C. difficile) infection, is a type of colitis caused by the overgrowth of C. difficile bacteria in the colon. This condition typically occurs after the use of broad-spectrum antibiotics, which disrupt the normal balance of gut flora.

**Why the Correct Answer is Right**
C. difficile produces toxins A and B, which damage the epithelial lining of the colon, leading to inflammation and the formation of pseudomembranes. The toxins interfere with the normal functioning of the cells, causing cell death and leading to the characteristic pseudomembranous colitis. The use of broad-spectrum antibiotics is a major risk factor for developing C. difficile infection, as it eliminates the normal flora that keeps C. difficile in check.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is not the primary cause of pseudomembranous colitis. While other bacteria can cause colitis, C. difficile is the most common and well-documented cause.
**Option B:** This option is incorrect because it is not a known cause of pseudomembranous colitis. While other infections can cause colitis, C. difficile is the specific organism associated with this condition.
**Option C:** This option is incorrect because it is not a known cause of pseudomembranous colitis. Other organisms may cause colitis, but C. difficile is the primary cause of pseudomembranous colitis.

**Clinical Pearl / High-Yield Fact**
It is essential to consider C. difficile infection in patients who have recently taken broad-spectrum antibiotics and present with diarrhea, abdominal pain, and bloody stools. A high index of suspicion and proper testing can lead to timely diagnosis and treatment.

**Correct Answer:** C. Clostridioides difficile