This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
.All are catalase positive except 
Select and explain. 
A. S. flexneri, B. S. boydii, C. S. dysenteriae type I, D. S. sonnei
C: S. dysenteriae type I
Answer: C: S. dysenteriae type I 
Explanation: All bacteria among the Enterobacteriaceae including Shigella species are catalase positive exceptShigella dysenteriae type I(Ref: Ananthanarayan 9th edition, p285)