This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: miscellaneous, Subject name: Microbiology
A person returns to Delhi from Bangladesh after 2 days and has diarrhoea. Stool examination shows RBC&;s in the stool. The likely organism is 
Select and explain. 
A. Enteropathogenic E. Coli, B. Enterotoxigenic E. Coli., C. Salmonella typhi, D. Shigella dysenteriae
D: Shigella dysenteriae
Answer: D: Shigella dysenteriae 
Explanation: Shigellae cause bacillary dysentery. Infection occurs by ingestion.The minimum infective dose is low-as few as 10-100 bacilli are capable of initiating the disease. Sho incubation period. Clinical features - Frequent passage of loose, scanty faeces containing blood and mucus along with abdominal cramps and tenesmus. Ref: Ananthanarayan and Paniker&;s Textbook of Microbiology, 9th edition; pg no: 286, 287