A child presents with infective skin lesion of the leg. A culture was done which showed gram+ve cocci in chains which were hemolytic colonies. The test to confirm the organism is
Bile solubility
Optochin sensitivity
Bacitracin sensitivity
Catalase positive
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 Maxted's 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 paniker's; 10th edition; Page no: 217
Bacteriology