Application

Kovac′s reagent for indoles has been used for enumerating E. coli O157:H7 in ground beef samples in different scenarios of stored, thawed, and as cooked patty samples. It has also been used for E coli enumeration in dewatered blackwater.

Biochem/physiol Actions

Kovac′s reagent detects the indole and aids in identifying the indole-positive and indole-negative microorganisms. E. coli can split tryptophan into indole and α-aminopropionic acid in the presence of the enzyme tryptophanase. p-Aminobenzaldehyde present in the reagent reacts with indole to form a cherry-red complex, that is soluble in alcohol, ether, and chloroform. It is recommended to use glucose free media and peptone with a high tryptophan content for the test.

General description

Kovac′s reagent for indoles is a solution of 4-(dimethylamino)benzaldehyde and hydrochloric acid in n-butanol.