Which organism yields a negative PYR test?

Unlock all questions

This demo includes only 20 questions. Upgrade to access hundreds of questions, flashcards, exam simulations, and disable ads.

Full question bankExam simulationsFlashcards
From $9.99Unlock all

Study for the Success! In Clinical Laboratory Science – Bacteriology Test. Enhance your skills with detailed questions, hints, and comprehensive explanations. Prepare confidently for success!

Multiple Choice

Which organism yields a negative PYR test?

Explanation:
The test hinges on detecting the PYR enzyme, pyrrolidonyl arylamidase. If an organism makes this enzyme, adding the PYR reagent leads to a color change indicating a positive result. Viridans streptococci typically lack this enzyme, so the reaction stays negative. This pattern helps separate the viridans group from organisms that do produce PYR, such as Streptococcus pyogenes (Group A strep) and Enterococcus species. In other words, a negative PYR result points toward viridans streptococci, while positive results would suggest the other organisms.

The test hinges on detecting the PYR enzyme, pyrrolidonyl arylamidase. If an organism makes this enzyme, adding the PYR reagent leads to a color change indicating a positive result. Viridans streptococci typically lack this enzyme, so the reaction stays negative. This pattern helps separate the viridans group from organisms that do produce PYR, such as Streptococcus pyogenes (Group A strep) and Enterococcus species. In other words, a negative PYR result points toward viridans streptococci, while positive results would suggest the other organisms.

More Multiple Choice Questions
Subscribe

Get the latest from Examzify

You can unsubscribe at any time. Read our privacy policy