This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'A young male patient has history of diarrhea 3-4 weeks back, now complaining of right knee pain, swelling in other joints with signs of inflammation and dactylitis. The most probable causative organism is \nSelect and explain. \nA. Shigella, B. Campylobacter, C. E coli, D. Yersinia', 'role': 'user'}, {'content': "Answer: A \nExplanation: Answer- a. ShigellaThis is a case of reactive ahritis.Most common cause of reacticve ahtis is chlamydia trachomatis.Reiter's syndrome is causedly preceding infection of genital tract by chlamydia trachomatis (M.C.) or GI tract by ShigellaSalmonella, Ureoplasma ureolyticum, Yersinia, Campylobacter", 'role': 'assistant'}]