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Pyrrolidonyl Arylamidase (PYR) Differential

As mentioned before, the spot pyrrolidonyl arylamidase (PYR) test is commonly performed to separate Enterococcus species (positive reaction) from the group D streptococci (S. bovis, S. equinus), which are negative.

It should be remembered that Streptococcus pyogenes (group A) also produces PYR; therefore, additional characteristics such as beta hemolysis are important. Some species of Aerococcus and Gemella are also PYR-positive; however, they can be suspected if large cocci in tetrads or clusters are observed on Gram stain. These species are rare isolates in most clinical practices.