Related Experiment Videos
Presumptive identification of streptococci by pyrrolidonyl-beta-naphthylamide (PYR) test
1Department of Pathology, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan, R.O.C.
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.