A 70-year-old hospitalised patient develops severe watery diarrhoea with 10 bowel movements per day, abdominal pain, and fever on day 8 of clindamycin therapy for aspiration pneumonia. Sigmoidoscopy reveals yellow-white plaques on the colon mucosa. Which virulence factor directly causes the mucosal damage in this condition?
- A Shiga-like toxin inhibiting protein synthesis in colonic epithelium
- B Clostridium perfringens enterotoxin disrupting tight junctions
- C Toxin A (enterotoxin) and Toxin B (cytotoxin) of Clostridioides difficile inactivating Rho GTPases ✓
- D Staphylococcal toxic shock syndrome toxin-1 acting as superantigen
Explanation
Clostridioides difficile (formerly Clostridium difficile) produces Toxin A (TcdA, enterotoxin) and Toxin B (TcdB, cytotoxin). Both are glucosyltransferases that inactivate Rho family GTPases (Rho, Rac, Cdc42) by glucosylation. Rho GTPases normally regulate actin cytoskeleton organisation and tight junction integrity; their inactivation leads to cytoskeletal collapse, disruption of the colonic epithelial barrier, neutrophil infiltration, and pseudomembrane formation. Toxin B is approximately 10-fold more cytotoxic than Toxin A. The binary toxin (CDT) of hypervirulent strains (NAP1/BI/027) additionally ADP-ribosylates actin. Stool enzyme immunoassay (EIA) for Toxin A+B, GDH antigen, or PCR confirms diagnosis. Treatment is oral vancomycin or fidaxomicin.
Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.