<prompt> A child presents with infective skin lesion of the leg. A culture was done which showed gramve cocci in chains which were hemolytic colonies. The test to confirm the organism isBile solubilityOptochin sensitivityBacitracin sensitivityCatalase positive  <response>: The culture is suggestive of infection with Streptococcus pyogenes which is gram-positive, occurring in chains and beta-hemolytic. A convenient method for the identification of Streptococcus pyogenes is based on Maxteds observation that they are more sensitive to bacitracin than other streptococci. Bacitracin sensitivity test: A filter paper disc of 0.04U is applied on the surface of an inoculated blood agar. After incubation, a wide zone of inhibition is seen with Streptococcus pyogenes and not with other streptococci. Reference: Textbook of Microbiology; Anathanarayan and panikers; 10th edition; Page no: 217 