This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Gram Positive Bacilli, Gram Negative Bacilli), Subject name: Microbiology
[{'content': 'Drug of choice for Cl. difficile ? \nSelect and explain. \nA. Metronidazole, B. Vancomycin, C. Rifampicin, D. Ciprofloxacin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Drug of choice is oral vancomycin and second drug of choice Metronidazole', 'role': 'assistant'}]