Oral vancomycin is mainly used for which condition?

• A. MRSA pneumonia
• B. Clostridioides difficile infection
• C. Pseudomonal bacteremia
• D. Streptococcal pharyngitis

Answer: (B)

Oral vancomycin is used for Clostridioides difficile infection because its poor absorption from the gut keeps it in the intestinal lumen, producing very high concentrations in the colon where C. difficile causes disease while minimizing systemic exposure. This gut-focused action makes it effective for CDI without relying on drugs that reach the bloodstream.

It wouldn’t be the right choice for MRSA pneumonia since treating pneumonia requires drug levels in the lungs from systemic administration; oral vancomycin wouldn’t reach the pulmonary tissue effectively. For Pseudomonal bacteremia, vancomycin doesn’t target Pseudomonas aeruginosa, which needs agents active against gram-negative rods. And for streptococcal pharyngitis, first-line therapy is typically a beta-lactam like penicillin or amoxicillin; vancomycin isn’t the preferred option there due to spectrum considerations and lack of need for a gut-restricted agent.