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': 'Which of the following organism can cause acalculous cholecystitis? \nSelect and explain. \nA. Leptospirosis, B. Malaria, C. Staphylococcus, D. Nocardiosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Precipitating factors for acalculous cholecystitis are vasculitis, obstructing adenocarcinoma of the gallbladder, diabetes mellitus, torsion of the gallbladder, "unusual" bacterial infections of the gallbladder (e.g., Leptospira, Streptococcus, Salmonella, or Vibrio cholerae). Reference: Harrisons Principles of Internal Medicine, 18th Edition, Page 2621', 'role': 'assistant'}]