Which of the following drug is active selectively against Anaerobic and Microaerophilic organisms ?
**Core Concept**
The question tests the student's knowledge of antimicrobial pharmacology, specifically the spectrum of activity of various antibiotics. **Metronidazole** is a key drug in this context, known for its efficacy against anaerobic and microaerophilic bacteria.
**Why the Correct Answer is Right**
Metronidazole works by entering the cells of anaerobic and microaerophilic organisms, where it is reduced to its active form, which then damages the DNA of the microbial cell, ultimately leading to cell death. This mechanism is highly selective for anaerobic and microaerophilic organisms because the reduction of metronidazole to its active form requires the low redox potential found in these cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because it is not specified and thus cannot be evaluated for its antimicrobial spectrum.
**Option B:** Incorrect as it is also unspecified, similar to option A.
**Option D:** Incorrect because, like options A and B, it lacks specificity regarding its antimicrobial activity.
**Clinical Pearl / High-Yield Fact**
A key point to remember is that **metronidazole** is particularly useful in treating infections caused by anaerobic bacteria, such as those found in abdominal abscesses or infections following abdominal surgery. Its selective activity against anaerobes makes it a valuable agent in scenarios where anaerobic infection is suspected.
**Correct Answer:** D. Metronidazole.