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
Salmonella typhi is the causative agent of typhoid fever. The infective does of S.typhi 
Select and explain. 
A. One bacillus, B. 108-1010 bacilli, C. 102-105 bacilli, D. 1-10 bacilli
C: 102-105 bacilli
Answer: C: 102-105 bacilli 
Explanation: Ans. is 'c' i.e., 102-105 bacilli In human volunteer experiments, the infective dose was found to be 103-106 bacilli. Organism Infective dose . ETEC . EIEC . EHEC . Shigella . Campylobactor jejuni . Yersinia enterocolitica . Vibrio 106-101deg 108-10m 10-100( 104 108-109 1010 (if source of infection is water) 102-104 (if source of infection is food)