This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteria, Subject name: Microbiology
Most virulent variety of shigellosis is caused by: 
Select and explain. 
A. S. dysentriae, B. S. sonnei, C. S. flexneri, D. S. boydii
A: S. dysentriae
Answer: A: S. dysentriae 
Explanation: Ans. is 'a' i.e., Shigella dysenteriae(Ref: Ananthanarayan, 8th/e, p. 286 and 9th/e, p. 2851)Complications are most often seen in infection with Sh. dysenteriae type I and include arthritis, toxic neuritis, conjunctivitis, parotitis and in children, intussusception. HUS may occur in severe cases.