**Core Concept**
Oral vancomycin is a glycopeptide antibiotic that acts by inhibiting cell wall synthesis in Gram-positive bacteria. It is effective against a broad spectrum of Gram-positive pathogens, including Clostridioides difficile, the primary cause of pseudomembranous colitis.

**Why the Correct Answer is Right**
Pseudomembranous colitis, also known as Clostridioides difficile-associated diarrhea (CDAD), is a condition characterized by inflammation of the colon and the formation of pseudomembranes. Oral vancomycin is the treatment of choice for CDAD because it is not absorbed systemically, allowing it to act locally in the gut and eliminate the causative bacteria. The high concentration of vancomycin in the colon effectively inhibits the growth of C. difficile, thereby reducing toxin production and alleviating symptoms.

**Why Each Wrong Option is Incorrect**
**Option A:** Oral vancomycin is not indicated for the treatment of hepatic encephalopathy, a condition characterized by cognitive dysfunction and altered mental status in patients with liver disease. Vancomycin does not have a role in the management of hepatic encephalopathy, which is typically treated with lactulose and/or rifaximin.

**Option C:** Oral vancomycin is not used for the treatment of Staphylococcal food poisoning, a condition caused by the ingestion of Staphylococcus aureus toxin. Antibiotics are not typically used to treat Staphylococcal food poisoning, as the disease is usually self-limiting and resolves on its own.

**Clinical Pearl / High-Yield Fact**
It is essential to note that oral vancomycin is not absorbed systemically, which makes it an effective treatment for CDAD without the risk of systemic toxicity. This unique property of oral vancomycin allows for targeted therapy against C. difficile, reducing the risk of antibiotic resistance.

**Correct Answer:**
✓ Correct Answer: B. Pseudomembranous colitis