Liofilchem® TBX Agar

TBX Agar is a selective chromogenic medium designed for the isolation, detection, and enumeration of Escherichia coli in food and related samples, as per ISO 16649 standards. It utilizes chromogenic substrates to allow visual differentiation of E. coli colonies from other organisms based on enzyme activity.

Key Features:

1. Chromogenic Substrate:
   • Contains 5-bromo-4-chloro-3-indolyl-β-D-glucuronide (BCIG), which is cleaved by E. coli β-glucuronidase to produce blue to blue-green colonies.
2. Selective Medium:
   • Bile Salts No. 3 inhibits Gram-positive bacteria while allowing E. coli to thrive.
3. ISO Compliance:
   • Conforms to ISO 16649-1, -2, and -3 for microbial testing in the food chain.
4. High Performance:
   • Provides reliable recovery of sub-lethally injured E. coli and effective differentiation of β-glucuronidase-positive E. coli from other organisms.

Typical Composition (per liter):

Preparation Instructions:

1. Dehydrated Medium:
   • Suspend 36.6 g of powder in 1 L of distilled or deionized water.
   • Mix well, heat to boiling while stirring until completely dissolved.
   • Sterilize by autoclaving at 121°C for 15 minutes.
2. Ready-to-Use Bottles:
   • Melt contents in a 100°C water bath (with partially loosened cap).
   • Once dissolved, tighten the cap, mix gently, and cool to 45–50°C.
   • Aseptically pour into Petri dishes.

Applications:

1. Enumeration of E. coli:
   • Ideal for food, feed, and environmental sample testing.
2. Quality Control:
   • Detection of β-glucuronidase-positive E. coli in compliance with ISO methods.
3. Microbial Analysis:
   • Suitable for direct or membrane filtration-based testing.

Test Procedure:

1. Sample Preparation:
   • Filter 1 mL of sample (or dilutions) onto a membrane filter placed on Mineral-Modified Glutamate Agar (MMGA).
   • Incubate at 37°C for 4 ± 1 hours.
2. Transfer to TBX Agar:
   • Transfer the membrane filter to a TBX Agar plate.
   • Incubate at 44°C for 18–24 hours.
3. Interpretation:
   • Count colonies with blue to blue-green coloration as β-glucuronidase-positive E. coli.
   • Non-E. coli colonies appear white to green-beige.

Interpretation of Results:

Quality Control:

Storage and Stability:

• Dehydrated Medium: Store at 10–30°C in a dry environment, tightly sealed.
• Ready-to-Use Bottles/Plates: Store at 2–8°C away from light.

Presentation:

Warnings and Precautions:

• The product is not classified as hazardous but is intended for professional use only.
• Consult the Safety Data Sheet (SDS) for proper handling and disposal.
• Waste disposal should follow national and local regulations.

This reliable medium ensures accurate detection and enumeration of E. coli in compliance with ISO standards, supporting microbiological analysis in food safety and quality assurance.