KOVAC?S INDOLE REAGENT

Kovac’s Indole Reagent is used to determine the production of indole by microorganisms. This test distinguishes bacterial species on the basis of their ability to degrade tryptophan. This degradation is catalysed by an enzyme called tryptophanase and results in the formation of indole.
The reagent is 4-dimethylaminobenzaldehyde in amyl alcohol and hydrochloric acid. The reagent reacts with indole formed by the microorganism when added to a suitable tryptophan-containing medium inoculated with an organism. A positive reaction is indicated by the appearance of a red ring at the interface of reagent and culture medium. The absence of a red ring indicates a negative reaction.
For example, Escherichia coli ATCC 25922 gives a positive reaction with the formation of a red ring, whereas Enterobacter aerogenes ATCC 13048 gives a negative reaction with no red ring. This reagent is thus helpful in the routine biochemical identification procedures in the laboratory of microbiology.
The reagent has a light yellow to light brown appearance. Proper laboratory practices should be followed during handling and testing to obtain consistent and reliable results.

A biochemical reagent used to detect indole production by microorganisms through formation of a characteristic red ring.