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Detect and enumerate Escherichia coli in food and animal feed samples with Thermo Scientific™ Oxoid™ Typtone Bile X-Glucuronide (TBX) Medium (Dehydrated). The medium meets the formulation and performance criterion laid down in ISO 16649 and ISO 11133:2014.

TBX Medium builds on the speed, reliability and recovery from frozen samples and detection of poor lactose fermenters offered by the original Tryptone Bile Agar, with the addition of a chromogenic agent, X-glucuronide, which detects glucuronidase activity, an enzyme shown to be highly specific for Escherichia coli.

Typtone Bile X-Glucuronide (TBX) Medium (Dehydrated), Oxoid Composition

Typtone Bile X-Glucuronide (TBX) Medium (Dehydrated), Oxoid Preparation:
Suspend 36.6g of TBX Medium in 1 litre of distilled water. Sterilise by autoclaving at 121°C for 15 minutes. Cool to 50°C and pour the medium into sterile Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates of medium at 2-8°C.

Oxoid Tergitol 7 Agar is used for the enumeration and identification of coliforms.

Tergitol 7 Agar, Oxoid Composition

TTC Solution (SR0148) is supplied as 2ml of filtered 0.125% aqueous solution of tri-phenyltetrazolium chloride (TTC).

Tergitol 7 Agar, Oxoid Preparation:
Suspend 54.15g in 1 litre of distilled water. Bring to the boil to dissolve completely. Dispense in 100ml volumes and sterilise by autoclaving at 121°C for 15 minutes. Cool to 50°C and add the contents of 1 vial of SR0148. Mix well and pour into sterile Petri dishes.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium at 2-8°C.

Precautions
Tergitol-7 Agar is designed for early detection of Escherichia coli i.e. 6-10 hours incubation.
Incubation at 44°C has been recommended.

Oxoid Tetrathionate Broth is used for the selective enrichment of Salmonella spp.

Tetrathionate Broth, Oxoid Composition

Tetrathionate Broth, Oxoid Preparation:
Suspend 46g in 1 litre of distilled water and bring to the boil. Cool to below 45°C and add 20ml of iodine-iodide solution immediately before use. Mix continuously whilst dispensing 10ml volumes into sterile tubes. Use the complete medium (with added iodine) on the day of preparation.

The base may be prepared beforehand and kept for several weeks at 4°C. Iodine-iodide solution can then be added at the time of use to the quantity of medium needed.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the base broth at 2-8°C. Use the medium immediately after adding the iodine solution.

Oxoid Tetrathionate Broth Base is used for selective enrichment of Salmonella species.

Tetrathionate Broth Base, Oxoid Composition
Add 77g to 1 litre of distilled water and bring to the boil. Cool below 45°C and add 20ml of iodine solution. Mix well and tube in 10ml quantities. The prepared base will keep for several weeks at 4°C but should be used soon after the addition of the iodine solution.

Iodine Solution

Tetrathionate Broth Preparation:
Tetrathionate Broth is recommended for the selective enrichment method of isolating Salmonella typhi and other salmonellae from faeces, sewage, etc.

Organisms which reduce tetrathionate, such as salmonellae, flourish in the medium whilst many faecal organisms are inhibited. Members of the Proteus group reduce tetrathionate and may consequently impair the value of this medium for the isolation of salmonellae; this disadvantage of the medium is largely overcome by the addition of 40µg of novobiocin to each millilitre of the incomplete medium before the addition of iodine.

Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared medium (without iodine solution) at 2-8°C.