Metronidazole is effective against these types of organisms except

• A. Aerobic
• B. Anaerobic
• C. Protozoan
• D. None of the above - Metronidazole is effective against all of the organisms stated above

Answer: (A)

Metronidazole activates only in anaerobic environments. Inside anaerobic organisms, its nitro group is reduced to active forms that damage DNA. Oxygen stops this activation, so aerobic organisms don’t get effective drug activity. That’s why metronidazole is powerful against anaerobic bacteria and many protozoa, but not against aerobic bacteria. Therefore, the organism type it does not work against is aerobic.