The drug causing pseudomembranous colitis:
**Core Concept**
Pseudomembranous colitis, also known as Clostridioides difficile (C. difficile) colitis, is a type of colitis caused by an overgrowth of the bacterium Clostridioides difficile in the colon. This condition often occurs as a complication of antibiotic use, which disrupts the normal gut flora, allowing C. difficile to overgrow and produce toxins that cause inflammation and damage to the colon.
**Why the Correct Answer is Right**
The correct answer is a type of antibiotic that is commonly associated with the development of pseudomembranous colitis. This is because broad-spectrum antibiotics can disrupt the normal balance of gut flora, allowing C. difficile to overgrow and produce toxins. The specific mechanism involves the inhibition of the normal gut flora, which normally competes with C. difficile for space and resources in the colon. When the normal flora is inhibited, C. difficile can overgrow and produce toxins that cause inflammation and damage to the colon.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because while it is also a broad-spectrum antibiotic, it is less commonly associated with pseudomembranous colitis compared to the correct answer.
**Option B:** This option is incorrect because it is not typically associated with pseudomembranous colitis, as it has a narrower spectrum of activity and is less likely to disrupt the normal gut flora.
**Option C:** This option is incorrect because it is not typically used to treat infections in the gut, and its use would not typically disrupt the normal gut flora.
**Clinical Pearl / High-Yield Fact**
It's essential to note that the use of broad-spectrum antibiotics increases the risk of developing pseudomembranous colitis, and it's crucial to consider this risk when prescribing these medications. A high-yield fact to remember is that metronidazole is often used as an initial treatment for mild to moderate C. difficile infection.
**Correct Answer:** A. Cephalosporins, especially those with a broad spectrum of activity, are commonly associated with pseudomembranous colitis due to their ability to disrupt the normal gut flora, allowing C. difficile to overgrow and produce toxins.