Pyrrolidonyl arylamidase test

• Used to identify group A streptococci and enterococci
• Principle: L-naphthylamide-β-naphthylamide in the test medium is hydrolyzed, releasing free β-naphthylamide. The reagent, N, N-dimethylaminocinnamaldehyde, is added. It joins with β-naphthylamid, if present, to form a red Schiff base.
• Procedure:
  • Select 2 to 3 colonies with a loop and emulsify into PYR broth
  • Incubate at 35ºC for 4 hours
  • Add one drop of PYR reagent and observe for color change
  • Read and record the reaction at 1 minute
• Interpretation
  • Deep red cherry within a minute of the addition of the reagent is positive
  • Yellow or orange color is negative
• Positive organisms include Streptococcus pyogenes and Enterococcus