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': 'In initial stages of typhoid, salmonella can be detected in: \nSelect and explain. \nA. Faeces, B. Urine, C. Blood, D. All of the above', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Blood culture: Blood culture is a very useful procedure for diagnosis of enteric fever. It is positive in approximately 90% of cases in the first week of fever, 75% of cases in the second week, 60% in the third week, and 25% thereafter till the subsidence of pyrexia. Blood cultures, however, rapidly become negative on treatment with antibiotics.\nParija SC. Textbook of Microbiology & Immunology. Elsevier Health Sciences; 2014. Page: 277', 'role': 'assistant'}]