This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Infection, Subject name: Medicine
[{'content': 'A 30-year-old man develops a pustular lesion at the site of a cat scratch on his forearm. This is followed 1 week later by malaise, fever, and lymphadenopathy. On examination, he has tender axillary lymph nodes. Which of the following is the most likely causative organism? \nSelect and explain. \nA. Bartonella henselae, B. Bartonella bacilliformis, C. Bartonella quintana, D. Coxiella burnetii', 'role': 'user'}, {'content': 'Answer: A \nExplanation: The cause of cat-scratch fever is a tiny Gram-negative bacillus, B. henselae. Cats acquire the organism from the soil and inoculate humans via scratches or bites. The disease is generally benign and self-limited, and is treated with analgesics and antipyretics. Encephalitis, seizures, coma, meningitis, and transverse myelitis can occasionally occur even in immunocompetent patients. A variety of antibiotics have been used when severe disease is present but an optimal regimen has not been identified.', 'role': 'assistant'}]