Overview

TBX Agar (Tryptone Bile X-glucuronide Agar) is a selective chromogenic culture medium designed for the rapid detection and enumeration of Escherichia coli in water, food, and environmental samples. The medium exploits the enzymatic activity of β-glucuronidase (GUD), which is produced by the vast majority of E. coli strains, to generate a distinct blue-green coloration upon hydrolysis of the chromogenic substrate X-glucuronide. TBX Agar is compliant with ISO 16649 for the enumeration of E. coli in food and animal feeding stuffs.

Principle of the Medium

Colony Appearance

Key Features & Benefits

Typical Applications

• Detection and enumeration of E. coli in drinking water, wastewater, and recreational water
• Food safety testing — dairy, meat, beverages, produce
• Environmental monitoring of surfaces and air in food production facilities
• Membrane filtration and pour plate enumeration workflows
• Quality control (QC) laboratories in food manufacturing and water utilities
• Research and teaching in applied and environmental microbiology

Preparation Guidelines

Technical Overview & Biochemistry

β-Glucuronidase (GUD, EC 3.2.1.31) is a lysosomal enzyme that cleaves the β-glycosidic bond of β-D-glucuronic acid conjugates. Approximately 94–97% of E. coli strains are GUD-positive, making GUD activity a highly reliable marker for this species. The uidA gene encodes GUD in E. coli, and its activity is constitutively expressed under the conditions used in TBX Agar. Bile salts (deoxycholate and cholate mixtures) act by disrupting the cytoplasmic membrane of Gram-positive bacteria while leaving Gram-negative organisms largely unaffected, providing a robust selective environment.

E. coli Detection Media Comparison

Cross-Reference / Equivalent Products

Storage & Shelf Life

• Store at 15–25°C in a dry location, away from heat and moisture
• Keep container tightly sealed when not in use
• Protect from direct light exposure
• Shelf life: stated on label; refer to COA for batch-specific expiry

Intended Use

For laboratory and research use only. Not for direct human, veterinary, or food additive use.

Marketing / Display Titles

• TBX Agar (AS-1427) – ISO 16649 Chromogenic Medium for E. coli Detection | AuSaMicS Australia
• Tryptone Bile X-glucuronide Agar – Rapid E. coli Confirmation in Water & Food Testing
• Australian-Made TBX Agar | β-Glucuronidase Chromogenic Detection Medium

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Download Product Description (PDF)

Technical Data Sheet (TDS) — AS-1427

The Technical Data Sheet for TBX Agar (AS-1427) covers physicochemical composition, quality control performance data, mode of action, and peer-reviewed literature references in accordance with AuSaMicS TDS Option 2 documentation standards.

Composition (per litre of prepared medium)

Physicochemical Specifications

Quality Control Performance

Mode of Action

TBX Agar operates through two complementary mechanisms. First, bile salts suppress the growth of Gram-positive organisms by disrupting their cytoplasmic membranes, providing selective enrichment of Gram-negative enteric bacteria. Second, the chromogenic substrate X-glucuronide (5-bromo-4-chloro-3-indolyl-β-D-glucuronide) is hydrolysed by β-glucuronidase (encoded by the uidA gene), an enzyme constitutively expressed by approximately 94–97% of E. coli strains at 44°C. The released indoxyl moiety spontaneously dimerises and oxidises to form an insoluble blue-green dye (5,5'-dibromo-4,4'-dichloro-indigo), precipitating at the colony site and providing direct visual confirmation of E. coli.

Literature References

• Manafi, M., & Ossmer, R. (1993). Fluorocult TBX Agar: a new chromogenic medium for the rapid detection of E. coli in water. Zentralblatt für Hygiene und Umweltmedizin, 194(4), 380–386.
• ISO 16649-2:2001. Microbiology of food and animal feeding stuffs — Horizontal method for the enumeration of β-glucuronidase-positive Escherichia coli. International Organisation for Standardisation, Geneva.
• Frampton, E.W., & Restaino, L. (1993). Methods for E. coli identification in food, water and clinical samples based on beta-glucuronidase detection. Journal of Applied Bacteriology, 74(3), 223–233.

Full TDS document (five-file documentation set: PD, TDS, SDS, COA + HTML embed) available as a downloadable PDF.

Download TDS (PDF)

Safety Data Sheet (SDS) — Summary

The full Safety Data Sheet for TBX Agar (AS-1427) is prepared in accordance with the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) and Australian WHS Regulations (Safe Work Australia), covering all 16 mandatory sections.

Full 16-section GHS-compliant SDS with embedded GHS pictograms available as a downloadable PDF.

Download SDS (PDF)

Certificate of Analysis (COA) — AS-1427

Each batch of TBX Agar (AS-1427) is produced under quality-controlled conditions and is released with a batch-specific Certificate of Analysis confirming compliance with AuSaMicS physicochemical and microbiological performance specifications.

COA — Typical Specifications

Batch Traceability

Batch-specific COA is issued at the time of dispatch and is available for download or provided as a physical document on request.

Download COA (PDF) Request Batch-Specific COA