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
[{'content': 'All are true about Shigella except: \nSelect and explain. \nA. Large dose is required for infection, B. Associated with hemolytic uremic Syndrome, C. Causes bloody diarrhea with mucus, D. Gut pathology is due to toxin.', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. is \'a\' i.e. Large dose is required for infection. * Shigella is highly communicable .The infective dose for shigella is less. It can be as low as 10 -100 bacilli because they survive gastric acidity better than other enterobacteriae.I had a hard time confirming the choice D.After going through Paniker Page 264 6th/e, Jawetz Page 224 22nd/e, Harrison Page 97615th/e I came to the conclusion that -r<r essential process in the pathogenesis is invasion of the mucosal epithelial cells by the organism through phagocytosis. The production of toxin is also of importance for virulence but main factor is invasion of the Epithelial cells of gut by the organism "REMEMBER: "Non toxigenic mutants can still cause dysentery but not noninvasive one"', 'role': 'assistant'}]