Can peptone water be used for indole test?
Like many biochemical tests on bacteria, results of an indole test are indicated by a change in color following a reaction with an added reagent. Pure bacterial culture must be grown in sterile tryptophan or peptone broth for 24–48 hours before performing the test.
What reaction does the tryptone broth test for?
Tryptone Broth is used for the detection of indole production by coliforms. Suspend 15 grams in 1000 ml distilled water. Heat if necessary to dissolve the medium completely. Dispense into tubes and sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes.
Is E coli indole positive?
Indole production is often used to differentiate E. coli from other indole-negative enteric bacteria because 96% of E coli are indole positive, whereas many enterobacterial species are negative in the indole reaction.
Can E coli be indole negative?
What does the indole test determine?
The indole test is a qualitative procedure for determining the ability of bacteria to produce indole by deamination of tryptophan. Using Kovacs method, indole combines, in the presence of a tryptophan rich medium, with p-Dimethylaminobenzaldehyde at an acid pH in alcohol to produce a red-violet compound.
How is tryptone water used to test for E coli?
Tryptone Water is used in conjunction with Brilliant Green Bile Broth 2% (M121) to determine the most probable number (MPN) of E.coli in food sample. Growth and gas production in M121 and indole production in Tryptone Water following incubation of both media at 44 ± 1°C is used as the basis for the presumptive E.coli test.
How do you test for indole in tryptone broth?
Inoculate the tube of tryptone broth with a small amount of a pure culture. Incubate at 35°C (+/- 2°C) for 24 to 48 hours. To test for indole production, add 5 drops of Kovács reagent directly to the tube (3, 5).
How do you test for indole in tryptophan?
To test for the presence of indole, a by-product of tryptophan metabolism, 5 drops of Kovács reagent should be added to the top of the deep. positive indole test is indicated by the formation of a red color in the reagent layer on top of the agar deep within seconds of adding the reagent.
What is tryptone water (m463i)?
Tryptone Water is recommended by APHA (1) for detection of indole production by coliforms, which is a key feature in differentiation of bacteria. A slight modification of Tryptone Water (M463I) is recommended by ISO committee (4) for the same purpose.