This test demonstrate the ability of certain bacteria to decompose the amino acid tryptophane to indole, which accumulates in the medium. Indole production test is important in the identification of
What is a positive indole test?
A positive indole test is indicated by the formation of a red color in the reagent layer on top of the agar deep within seconds of adding the reagent. If a culture is indole negative, the reagent layer will remain yellow or be slightly cloudy.
Why do bacteria produce indole?
Indole is a direct product of amino acid catabolism, signals in multidrug exportation, cell division inhibition, stresses resistance, and biofilm formation (this review).
