This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bacteriology, Subject name: Microbiology
[{'content': 'A child presents with infective skin lesion of the leg. Culture showed hemolytic colonies which were gram + ve cocci in chains. The test to confirm the organism is \nSelect and explain. \nA. Optochin sensitivity, B. Bile solubility, C. Catalase positive, D. Bacitracin sensitivity', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Hemolytic colonies with gram-positive cocci in chains suggest either alpha or beta-hemolytic streptococci. Bacitracin sensitivity is used to differentiate between streptococci as follows: Group A: Bacitracin sensitive Group B: Bacitracin resistant Bile solubility and optochin sensitivity are used to differentiate Pneumococcus and Streptococcus viridans Catalase test is used to differentiate Streptococcus and Staphylococcus Reference: Ananthanarayan and Paniker&;s Textbook of Microbiology Tenth edition', 'role': 'assistant'}]