A collection of reagents and other associated materials intended to be used for the qualitative and/or (semi-)quantitative detection of pyrrolidonyl arylamidase (PYR) activity in a clinical specimen and/or culture isolate within a short period, relative to standard laboratory testing procedures, using a rapid colorimetric method. This is a rapid test used in the laboratory or in point-of-care analyses typically to differentiate Group A streptococci and enterococci from Group D streptococci. It is not intended to be used for self-testing.