Presumptive identification of streptococci by pyrrolidonyl-beta- naphthylamide (PYR) test

Background. Group A streptococci and enterococci can be differentiated from other streptococci on the basis of their ability to cleave L- pyrrolidonyl-beta-naphthylamide. Methods. In the present study, the L- pyrrolidonyl-beta-naphthylamide (PYR) test, pigment medium and bile esculin medium have been used to presumptively identify the streptococci. In total, 114 strains of group A streptococci, 350 strains of non-group A streptococci, 202 strains of enterococci and 197 strains of non-enterococci have been tested. Results. The results of the present investigation show that sensitivities of different test methods are: PYR broth, 99.08%; Murex PYR, 98.48%; bacitracin, 95%; bacitracin and sulfamethoxazole/trimethoprim (SXT), 95%; pigment medium, 99.23%; bile esculin medium, 99.26%. Additionally, specificities of various tests are: PYR broth and Murex PYR, 99.82%; bacitracin, 90.90%; bacitracin and SXT, 98.87%; pigment medium and bile esculin medium, 100%, respectively. Conclusions. PYR test has been observed to be very easy to use and may hence be considered as a rapid, reliable and cost-effective method for presumptive identification of group A streptococci and enterococci in the clinical laboratory.