Pyrrolidonyl Aminopeptidase
(PYR)

Uses:

1) It is used for the presumptive identification of group A streptococci (Streptococcus pyogenes).

2) It is used for the rapid differentiation of enterococci from group D ß-hemolytic streptococci.

3) It also differentiate some Staphylococci (positive haemolyticus from negative S. auricularis).

4) Sample type: Colonies from pure culture.

5) Precautions: sterile the loop

6) And don’t take any sample without label.

Interfering factors:

1) A false-negative test can result if the disk or filter paper are too moist.

2) False-negative tests can result if selective media or tube biochemical agars are used to provide inocula.

3) Escherichia coli and indole-positive Proteus obtained from media containing a high tryptophan content may yield a blue-green color development. This is a negative result.

4) Some less commonly encountered isolates of lactococci and aerococci may be PYRase positive.

5) Non-specific colour reactions may occur if results are read after 20 seconds.

Pre analytical errors:

Sample preparation

Unlabeled sample

Post errors:

Sent results to incorrect patient.

Delayed report.

Corrective action:

Reject unlabeled sample