PYR Disc Test
The PYR Disc Test is used to detect the hydrolysis of L-pyrrolidonyl-ß-naphthylamide (PYR). The hydrolysis of PYR provides a valuable differential parameter to aid in the presumptive identification of Group A Streptococcus and Group D Enterococcus and provide differentiation from other Streptococcus and Group D Non-Enterococcus from pure culture.
The identification of Streptococcus and Enterococcus is necessary to diagnose clinical infections, initiate appropriate antimicrobial therapy, provide insight into the origin of the infection, and provide valuable information concerning the prognosis of the disease process.
Traditionally, the identification of clinically significant Streptococcus and Enterococcus has involved parameters such as hemolysis; resistance to such selective agents as bacitracin, optochin, trimethoprim / sulfamethoxazole and bile salts; hydrolysis of esculin and sodium hippurate; the CAMP reaction; and salt tolerance (3,5).
Utilizing “PYR” reaction, the PYR Disc Test provides a valuable differential parameter to aid in the presumptive identification of Group A Streptococcus and Group D Enterococcus. Investigators have reported that a positive PYR test provides excellent presumptive identification of Group A Streptococcus and Group D Enterococcus. The remaining Streptococcus groups demonstrate a negative PYR test (1,2,4)
The by-products of metabolized PYR (L-pyrrolidonyl-ß-naphthylamide) react with Indole (Sutter’s) Reagent (N,N-dimethylaminocinnaldehyde) to form an immediate bright-red complex. A negative reaction demonstrates no color reaction or a slow dull, pink complex; A positive reaction usually results in a formation of pink color within 30 seconds.
The PYR Disc Test uses a paper disc which is infused with L-pyrrolidonyl-ß-naphthylamide. The ability and inability of a test isolate to metabolize PYR is determined after addition of the Indole (Sutter’s) Reagent. Utilizing this paper-disc technology provides a standardized and stable test parameter, thus eliminating the need for bacitracin sensitivity, bile esculin, and 6.5% salt tolerance parameter.
SDS | Package Insert