Clostridium difficile: Pseudomembranous Colitis, Antibiotic-Associated Diarrhea.

Question 1

Pseudomembranous colitis

Answer 1

Pseudomembranous colitis is a severe colonic disease caused by Clostridium difficile overgrowth following antibiotic use (especially clindamycin, cephalosporins, ampicillin). Normal gut flora are suppressed, allowing C. difficile to proliferate and produce two key toxins: Toxin A (an enterotoxin that causes fluid secretion and mucosal inflammation) and Toxin B (a cytotoxin that causes cytoskeletal disruption and cell death). These toxins lead to mucosal ulceration and the formation of pseudomembranes—yellow-white plaques composed of fibrin, neutrophils, and necrotic debris. Clinical features include fever, abdominal cramps, leukocytosis, and profuse, sometimes bloody diarrhea. Severe cases may result in toxic megacolon, perforation, and death.

Question 2

Antibiotic-associated diarrhea

Answer 2

C. difficile can cause milder antibiotic-associated diarrhea without full pseudomembranous colitis. This occurs when antibiotics disrupt the normal intestinal flora, allowing overgrowth of C. difficile which releases toxins A and B, leading to inflammation and watery diarrhea. It is most commonly associated with antibiotics like clindamycin, cephalosporins, fluoroquinolones, and ampicillin. Diarrhea may begin during or after antibiotic therapy. Diagnosis is confirmed by detecting toxins (not just the organism) in stool using ELISA or PCR. Stopping the inciting antibiotic and beginning specific therapy for C. difficile (e.g., oral vancomycin or fidaxomicin) usually resolves the symptoms.