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
[{'content': 'A 12-year-old boy, after a camping trip near a wooded area in Northern California, is taken to the emergency room after complaining of a headache. He has an erythema migrans rash around what appears to be a tick bite. Which of the following is the antibiotic of choice for treating this patient? \nSelect and explain. \nA. Ampicillin, B. Ceftriaxone, C. Erythromycin, D. Penicillin', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Campylobacter difficile causes toxin-mediated pseudomembranous enterocolitis as well as antibiotic-associated diarrhea. Pseudomembranous enterocolitis is normally seen during or after administration of antibiotics. One of the few agents effective against C. difficile is vancomycin. Alternatively, bacitracin can be used.', 'role': 'assistant'}]