Strep Media Q. What additional tests can I do to confirm Group A Strep?
A. False-positives will often be encountered when using bacitracin discs to identify group A strep (up to 15%), because groups C and G will often be inhibited by bacitracin as well. Use the more specific PYR (Cat. no. Z75) method to confirm. Studies have shown PYR to have a specificity of 98% for S. pyogenes (ref: J. Clin. Micro., Vol. 15:987, 1982). It produces an instantaneous color change to red if positive. PYR is also a rapid way to assist in confirming Enterococcus faecalis, which will also be positive.
