Tryptone Bile X (TBX) Agar

//Tryptone Bile X (TBX) Agar

Tryptone Bile X (TBX) Agar

SKU: KM0162 Category:

Recent developments in culture media have given rise to the use of chromogenic substrates as a means of differentiating bacteria

particularly among the coliform group of organisms. This is one such medium and has been developed as a selective medium for the isolation and enumeration of Escherichia coli without the need for membranes or pre-incubation. Based on the formulation of Tryptone Bile Agar it incorporates a chromogenic substrate, X-Glucuronide, to detect the ß-glucuronidase enzyme which is specific for the majority of E. coli strains. Approximately, 3-4% of E. coli are glucuronidase negative including E. coli O157.(1) The advantage of the chromogenic substrate is that the reaction is concentrated within the colony resulting in distinctive blue/green colonies of E. coli while the other coliforms produce cream colonies.

The tryptone provides the required carbon, nitrogen and vitamins. Bile salts No.3 is a selective agent against Gram-positive bacteria. X-glucuronide is a chromogenic substrate. Agar is solidifying agent.

Additional Information


Shelf Life (days)

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Dehydrated Medium Appearance

Prepared Medium Appearance

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Prepared PH

Product Description

OrganismRef. No.Result
Escherichia coliNCTC 13216Growth, blue/green colonies
Enterobacter aerogenesNCTC 10006Growth, cream colonies
Enterococcus faecalisNCTC 12697Inhibited
Citrobacter freundiiATCC 43864Growth, white colonies
Pseudomonas aeruginosaNCTC 12903Growth, green-beige colonies


Bile salts no. 31.5


Suspend 36.6 g 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.