A child had pustular lesion on leg. On gram staining gram positive cocci are seen. To establish the diagnosis of Group A beta streptococcal pyoderma, the test used is:
High-Yield Explanation
Group A beta streptococcus produces pyogenic infections with a tendency to spread locally, along lymphatics and through the bloodstream. The growth of Str. pyogenes on agar plates in the laboratory is inhibited by the antibiotic bacitracin, an impoant diagnostic criterion. Sensitivity to bacitracin is a convenient method for differentiating Group A streptococcus from other hemolytic streptococci. Laboratory tests for group A beta streptococcus: Bacitracin sensitive PYR (pyrrolidonyl naphthylamide) test positive Ribose not fermented Ref: Ananthanarayan and Paniker's Textbook of Microbiology By Ananthanarayan And Paniker, 7th edition, Page 205.