Because the bacitracin test is not very specific for S pyogenes, it has been replaced in many laboratories by the ☆pyrrolidonyl arylamidase (PYR) test; S pyogenes is PYR-positive.
PYR positive→ GAS, ☆enterococci
PYR negative→ GBS, streptococcus gallolyticus (bovis)
*enterococci→ grow in bile and 6.5% NaCl
bovis→ grow in bile but not 6.5% NaCl
microbiology
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