Tryptone water is recommended for the detection of Escherichia coli in food and water samples. Tryptone water is an alternative medium to peptone water and is more reliable for the testing of indole production.
Tryptone acts as source of carbon, nitrogen and vitamins in this medium and sodium chloride maintains osmotic balance. The medium has a high content of tryptophan that many organisms, particularly coliforms, break down to form indole. After the recommended incubation indole positive organisms will give a distinct colour change when either Kovac’s or Ehrlich’s indole reagent is added.
KM0029 – Tryptone Water
Additional Information
| Shelf Life (days) | |
|---|---|
| Storage Temp (°C) | |
| Dehydrated Medium Appearance | |
| Prepared Medium Appearance | |
| Dehydrated Medium Colour | |
| Prepared Medium Colour | |
| Dehydrated PH | |
| Prepared PH | |
| Recommended Incubation |
Product Description
| Organisms | Ref. No | Result |
| Escherichia coli | NCTC 12241 | Turbid growth, indole positive |
| Enterobacter aerogenes | NCTC 10006 | Turbid growth, indole negative |
Formula*
| g/L | |
| Tryptone | 10.0 |
| Sodium chloride | 5.0 |
| Total | 15.0 |
| *Adjusted/supplemented as required to meet performance requirements | |
Preparation
Suspend 15g of the medium in one litre of deionised / purified water. Allow the medium to soak whilst mixing for 10 minutes. Sterilise at 121°C for 15 minutes with frequent stirring to completely dissolve the medium. Cool to 45-50°C and dispense into appropriate sterile containers.
