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': 'Which rickettesiae are able to grow in cell free media? \nSelect and explain. \nA. R. Quintana, B. R. Rickettsii, C. R. Typhi, D. R. Tsutsugamushi', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., R. Quintana . Rickettisiae are obligate intracelluar organisms. So they cannot grow in cell free medium. But, there is one exception to this rule, R. Quintana which is not an intracellular parasite, so can grow in cell free media.", 'role': 'assistant'}]