Which antibiotic is NOT considered first-line for mild-to-moderate C. difficile infection?

• A. Metronidazole
• B. Fidaxomicin
• C. Oral vancomycin
• D. Daptomycin

Answer: (A)

The key idea is choosing CDI therapy that gives the best cure rates with the lowest risk of recurrence for mild-to-moderate disease. The current preferred first-line options are oral vancomycin or fidaxomicin because they achieve higher cure rates and reduce relapse compared with older regimens. Metronidazole used to be common for mild cases, but it is no longer considered first-line due to lower efficacy and higher relapse rates. Daptomycin, on the other hand, has no activity against C. difficile, so it isn’t a viable option for this infection. That’s why metronidazole isn’t first-line in this context.