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: Microbiology
A child had pustular lesion on leg. On grainstaining gram positive cocci are seen. To establish the diagnosis of Group A streptococcal erythroderma, the test used is 
Select and explain. 
A. >Bile solubility test, B. >Catalase test, C. >Optochin sensitivity, D. >Bacitracin sensitivity
D: >Bacitracin sensitivity
Answer: D: >Bacitracin sensitivity 
Explanation: Bacitracin sensitivity (Ref: Harrison 16thle p 741, Anantnatyan] Streptococcal erythroderma is caused by streptococcus pyogenus Streptococcus pyogenus is b hemolytic streptococci and is Bacitracin positive.