This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Systemic Bacteriology (Haemophilus, Yersinia, Spirochaetes, Ricketssia, Chlamydia, Mycoplasma and Miscellaneous Bacteria), Subject name: Microbiology
[{'content': 'Which of the following statements is true about endemic typhus: \nSelect and explain. \nA. ls caused by R. rickettsii, B. ls transmitted by bites of fleas, C. Has no Mammalian reservoir, D. Can be cultured in chemical defined culture medium', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Option 1, 2, 3 Endemic typhus: Causative agent- R. typhi Vector - Flea, Rats are the reservoir Option 4 Rickettsiae cannot be cultivated in cell free media. Isolation can be done by cell lines (Vero, primary chick embryo, WI-38, HeLa), egg (yolk sac inoculation), or animal inoculation (guinea pig).', 'role': 'assistant'}]