Which statement about fidaxomicin is true?

Which statement about fidaxomicin is true?

• A. It is broad-spectrum against Gram-negative rods
• B. It is used for C. difficile infection and has lower recurrence than vancomycin
• C. It inhibits cytochrome P450
• D. It is not effective against C. difficile

Answer: (B)

Fidaxomicin is a narrow-spectrum antibiotic specifically used for Clostridioides difficile infections. It works by inhibiting the sigma subunit of RNA polymerase, which blocks transcription in C. difficile. Because it is poorly absorbed from the gut, it reaches very high concentrations in the colon where the infection resides, while largely sparing the rest of the gut microbiota. This targeted action helps prevent disruption of other beneficial bacteria, which is thought to reduce the risk of recurrence after treatment. It does not inhibit cytochrome P450 enzymes, so drug interactions are limited, and its activity is not broad-spectrum against Gram-negative rods. Therefore, the statement that fidaxomicin is used for C. difficile infection and has lower recurrence than vancomycin is true.

Fidaxomicin is a narrow-spectrum antibiotic specifically used for Clostridioides difficile infections. It works by inhibiting the sigma subunit of RNA polymerase, which blocks transcription in C. difficile. Because it is poorly absorbed from the gut, it reaches very high concentrations in the colon where the infection resides, while largely sparing the rest of the gut microbiota. This targeted action helps prevent disruption of other beneficial bacteria, which is thought to reduce the risk of recurrence after treatment. It does not inhibit cytochrome P450 enzymes, so drug interactions are limited, and its activity is not broad-spectrum against Gram-negative rods. Therefore, the statement that fidaxomicin is used for C. difficile infection and has lower recurrence than vancomycin is true.