Procedure to carry out Indole test:
o
Inoculate the tryptophan broth with the test organism and incubate at 37°C for 24-28h.
o
Add 0.5mL of the Kovac’s reagent and gently agitate
o
Examine the upper layer of liquid
Positive result red
colour (occurring within a few seconds)
Negative result yellow
colour
o
Moisten a piece of filter paper with the spot test reagent and smear a colony on to the
surface
o
Examine immediately
Positive result Green/blue
colour
Negative result No colour
change
