This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
All Clostridia cause myonecrosis except- 
Select and explain. 
A. C septicum, B. C difficle, C. Cnovyi, D. C welchii
B: C difficle
Answer: B: C difficle 
Explanation: Ans. is 'b' i.e., C difficle o Anaerobic myonecrosis (gas gangrene) is caused by-Cl perfringens (Cl welchii) - most common (80%)Cl SepticumCl novyiCl histolyticumo Cl difficle causes Clostridium difficle-associated disease (CDAD) which also includes pseudomembranous enterocolitis.