A 5-year-old child from a rural area presented to the OPD with pustular lesions on the lower legs. The cuture from the lesion showed hemolytic colonies on the blood agar which were Gram-positive cocci. Which of the following reactions would help to provisionally confirm the diagnosis of group A streptococcal pyoderma?
Optochin sensitivity
Bacitracin sensitivity
Catalase positivity
Bile solubility
Answer: b. Bacitracin sensitivity (Ref Ananthanaravan 8/e pe p205-206)Gram-positive cocci with alpha hemolytic colonies on sheep agar are Streptococcus viridians and Streptococcus pneumoniae.They can be fuher differentiated on basis of optochin sensitivity, Streptococcus viridians-optochin resistantor Streptococcus pneumonia-optochin sensitive.