Strep D Strips

Rapid diagnostic test for Group D streptococci based on aesculin hydrolysis.

Strep D Strips are a simple, inexpensive test for demonstrating aesculin hydrolysis performed on colonies taken directly from isolation plates. Results are available much faster than with traditional bile aesculin tests and can be used to distinguish Lancefield Group D streptococcus from other streptococci. The test works by demonstrating an organism’s ability to hydrolyse the glycoside aesculin in the presence of bile. Material from a colony is simply smeared on the strip which is then incubated at 37°C. The strips contain aesculin, ferric citrate, and bile salts. The aesculin is hydrolysed to aesculetin and glucose, and the aesculetin reacts with the ferric citrate to form the visible dark brown or black complex which indicates a positive reaction. A result will be available within 4 hours, and a good positive may be seen after 1 hour.

Description: Paper strip impregnated with aesculin and indicator.

Method of use: Using wire or plastic loop, touch 2 or 3 colonies of test organism on agar medium. Smear organism onto strip. Incubate for up to 4 hours at 37°C. Positive result is indicated by smeared area turning from buff colour to deep brown or black.

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