1. Label the strain of bacteria and date on the tube containing tryptone broth.
2. Inoculating each bacterial strain into its labeled tube.
3. Incubate tube at 37oC for 24 hours.
4. Determine the result by:
a. Add 1 ml of Kovac’s reagent into each culture tube and gently agitated.
b. Examine the color of the reagent layer in each culture.
c. Culture producing a red reagent layer following addition of Kovac’s reagent are indole-positive. The absence of red coloration demonstrates that substrate tryptophan was not hydrolyzed and indicates an indole-negative reaction