Description
Tryptone Water is an indole-test broth used for presumptive identification and enumeration of Escherichia coli.
Casein digest supplies tryptophan, which indole-producing organisms convert to indole. Kovac's reagent produces a red-to-purple surface ring in positive cultures.
A pure culture is incubated at 35 ± 2°C for 18–24 hours before Kovac's reagent is added. The surface colour reaction is interpreted according to the relevant food or water method.
