Streptococcus pyogenes can be presumptively identified using which disk?

Streptococcus pyogenes can be presumptively identified using which disk?

• A. Optochin disk
• B. PYR disk
• C. ONPG disk
• D. SPS disk

Answer: (B)

The main idea is that Streptococcus pyogenes (group A strep) is PYR positive, meaning it produces the enzyme pyrrolidonyl arylamidase. Using a PYR disk, the substrate is hydrolyzed and a red color develop quickly if the organism is PYR positive, giving a fast presumptive identification of S. pyogenes in the lab. The other disks target different organisms or tests: optochin disk identifies Streptococcus pneumoniae (optochin sensitive), which would not indicate S. pyogenes. ONPG disk tests for beta-galactosidase activity and isn’t used for routine strep ID. SPS disk has other用途 and isn’t the standard presumptive test for group A strep. So, the PYR disk provides the most specific quick indication for presumptive identification of Streptococcus pyogenes.

The main idea is that Streptococcus pyogenes (group A strep) is PYR positive, meaning it produces the enzyme pyrrolidonyl arylamidase. Using a PYR disk, the substrate is hydrolyzed and a red color develop quickly if the organism is PYR positive, giving a fast presumptive identification of S. pyogenes in the lab.

The other disks target different organisms or tests: optochin disk identifies Streptococcus pneumoniae (optochin sensitive), which would not indicate S. pyogenes. ONPG disk tests for beta-galactosidase activity and isn’t used for routine strep ID. SPS disk has other用途 and isn’t the standard presumptive test for group A strep.

So, the PYR disk provides the most specific quick indication for presumptive identification of Streptococcus pyogenes.