Few-minutes tests for the identification of group A streptococci and enterococci with chromogenic substrates.

The usefulness of paper strip tests for rapid identification of Streptococcus pyogenes and enterococci cultured on blood agar plates was investigated. The paper strips used contain dried chromogenic substrates for pyrrolidonyl peptidase (PYRase) and beta-glucosidase (beta-Gluc). Material from only a few colonies needed to be applied to the test strips. The reactions could be read after two min (PYRase) and 5-7 min (beta-Gluc), respectively. Results from testing 503 streptococcal strains were evaluated. The reactions proved very useful for rapid differentiation of S. pyogenes and enterococci from human sources. Nearly all strains of these streptococcal species showed positive reactions in the PYRase test whereas only the enterococci (E. faecalis and E. faecium) were positive for both enzymes.