This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Spirochetes, Subject name: Microbiology
[{'content': "Which among the following organism can't be demonstrated by gram staining? \nSelect and explain. \nA. Borrelia, B. spirochetes, C. Strep.pneumoniae, D. Mycoplasma", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans: b) SpirochetesBorrelia- gram negativeStrep pneumonia- gram positiveMycoplasma- gram negativeGram positive bacteria becomes gram negative when the cell wall is damaged.Even though spirochetes are grouped under gram negative organism, it is not a preferred test for diagnosing spirochetal disease.', 'role': 'assistant'}]