Which of the following species of clostridium causes pseudomembranous colitis?
**Core Concept**
Pseudomembranous colitis, also known as Clostridioides difficile (C. diff) infection, is a type of bacterial overgrowth in the colon that leads to inflammation and damage to the intestinal lining. This condition is often associated with the use of broad-spectrum antibiotics.
**Why the Correct Answer is Right**
Clostridioides difficile (previously known as Clostridium difficile) is a Gram-positive, anaerobic bacterium that produces toxins A and B, which cause the characteristic pseudomembrane formation and inflammation in the colon. The toxins disrupt the normal intestinal flora, leading to the overgrowth of C. diff. Infection with C. diff is often a result of antibiotic use, which disrupts the balance of the normal gut microbiota, allowing C. diff to overgrow and produce toxins.
**Why Each Wrong Option is Incorrect**
* **Option A:** Clostridium perfringens is a Gram-positive, anaerobic bacterium that produces toxins, but it is primarily associated with gas gangrene and food poisoning, not pseudomembranous colitis.
* **Option B:** Clostridium tetani is a Gram-positive, anaerobic bacterium that produces tetanospasmin, the toxin responsible for tetanus, a neurological disorder characterized by muscle stiffness and spasms.
* **Option D:** Clostridium botulinum is a Gram-positive, anaerobic bacterium that produces botulinum toxin, which causes botulism, a neurological disorder characterized by muscle weakness and paralysis.
**Clinical Pearl / High-Yield Fact**
C. diff infection is often associated with recent antibiotic use, hospitalization, or exposure to healthcare settings. A key risk factor is the use of broad-spectrum antibiotics, which disrupt the normal intestinal flora and allow C. diff to overgrow.
**Correct Answer:** C. Clostridioides difficile (C. diff) is the species responsible for causing pseudomembranous colitis.