Microbiology Salmonella typhi is the causative agent of typhoid fever. The infective dose of S. typhi is: A One bacillus B 108 - 1010 bacilli C 102 - 105 bacilli D 1 - 10 bacilli 💡 Explanation Salmonella typhi is the causative agent of typhoid fever. The infective dose of S. typhi is: ✓ Correct Answer: C. 102 - 105 bacilli