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': 'Salmonella typhi is the causative agent of typhoid fever. The infective dose of S. typhi is: \nSelect and explain. \nA. One bacillus, B. 108 - 1010 bacilli, C. 102 - 105 bacilli, D. 1 - 10 bacilli', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Ans. (c) 102 - 105 bacilli Infective dose of salmonella varies from 200 to 106 colony forming units and the ingested dose is an impoant determinant of incubation period Organism Infective dose Shigella 10 - 1000 Vibrio >1010 (if source of infection is water) 102- 104 (if source of infection is food) Campylobacter jejuni 104 Yersinia enterocolitica 108- 109 EHEC 10 - 100', 'role': 'assistant'}]