Pyrrolidonyl arylamidase (PYR)
DESCRIPTION
Pyrrolidonyl arylamidase test is used in the rapid identification of beta-hemolytic streptococci, especially
Streptococcus pyogenes, and
most strains of enterococci. Other bacteria like
Staphylococcus lugdunensis can also be PYR-positive.
The substrate in the PYR test is L-pyrrolidonyl-beta-naphtylamide. The enzyme hydrolyses the substrate to free beta-naphtylamide
and L-pyrrolidone. The reagent p-dimethylaminocinnamaldehyde couples with naphtylamide to produce a red product.


REAGENTS
PYR broth containing L-pyrrolidonyl-beta-naphtylamide,
PYR reagent containing p-dimethylaminocinnamaldehyde.

Note: PYR filter paper or disks are commercialy available also.


PROCEDURE
Emulsify 2-3 colonies of the tested strain in 0.2 ml of PYR broth and incubate the tube at 37 ºC for 4 hours.
Add 1 drop of PYR reagent, wait 1 minute and observe the color change.


RESULTS
Positive results if a deep cherry red color is produced. A yellow or orange color is considered negative result.


QUALITY CONTROL
Positive control:
Streptococcus pyogenes or Enterococcus faecalis.
Negative control: Streptococcus agalactiae.


REFERENCES:
1. Paul G. Engelkirk, Janet L. Duben-Engelkirk 2008. Laboratory Diagnosis of Infectious Diseases: Essentials of Diagnostic
Microbiology, pg. 708.
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