The L-pyrrolidonyl-B-napthylamide (PYR) hydrolysis test is used for which group of streptococci?

The L-pyrrolidonyl-B-napthylamide (PYR) hydrolysis test is specifically used to identify Group A streptococci (Streptococcus pyogenes) due to their ability to hydrolyze PYR. This test is also useful in differentiating members of Enterococcus species that belong to Group D streptococci, which also demonstrate positive reactions in this test. The ability to hydrolyze PYR is a key differentiating factor for these groups, making this test particularly valuable in clinical microbiology for accurate identification.

Group B streptococci (Streptococcus agalactiae), on the other hand, do not produce a positive reaction in the PYR test, which helps clarify the distinction between these groups. Additionally, nongroup A or B streptococci and Streptococcus pneumoniae do not show the same hydrolytic ability as Group A and D streptococci, thus this test is not applicable for these organisms. Therefore, recognizing the specificity of the PYR hydrolysis test for Groups A and D is crucial for accurate identification in a clinical setting.