This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Microbiology
[{'content': 'Organisms that has not been cultured successfully so far is - \nSelect and explain. \nA. Leptospira, B. Treponema pallidum, C. Bordetella, D. Staphylococcus', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., Treponema pallidum", 'role': 'assistant'}]