Liofilchem™ Tryptone Soy Yeast Extract Agar (TSYEA)

The Liofilchem™ Tryptone Soy Yeast Extract Agar (TSYEA) is a high-quality non-selective culture medium specifically designed for the confirmation and enumeration of Listeria monocytogenes and other Listeria species in food and environmental samples. It complies fully with ISO 11290-1 and ISO 11290-2 standards, making it an essential medium in standardized Listeria testing workflows.

TSYEA is typically used as a confirmation medium following isolation on selective agars such as Oxford or PALCAM, enabling clear observation of colony morphology and supporting downstream identification procedures.

Key Features

• Designed for confirmation and enumeration of Listeria spp.
• Compliant with ISO 11290-1 and ISO 11290-2 methods
• Supports reliable growth and characteristic colony morphology
• Suitable for food, environmental, and industrial microbiology
• Available in dehydrated powder, ready-to-use plates, and bottles
• Provides consistent performance for routine quality control testing

Applications

• Confirmation of Listeria colonies from selective media (Oxford, PALCAM)
• Enumeration of Listeria monocytogenes in food products
• Microbiological testing in food processing environments
• Quality control in pharmaceutical and industrial laboratories
• Compliance with international food safety standards

Method Principle

• Enzymatic digest of casein & soybean meal: Provide essential nutrients (amino acids, nitrogen, vitamins)
• Yeast extract: Rich source of B-group vitamins to enhance growth
• Sodium chloride: Maintains osmotic balance
• Dipotassium phosphate: Acts as a buffering agent
• Glucose: Fermentable carbohydrate for energy
• Agar: Solidifying agent

This balanced formulation supports optimal growth and differentiation of Listeria spp.

Typical Composition (g/L)

Preparation

Dehydrated Medium:

• Suspend 49 g/L in distilled or deionized water
• Heat to boiling until fully dissolved
• Sterilize at 121°C for 15 minutes

Prepared Medium (Bottles):

• Melt in water bath at 100°C
• Cool to 45–50°C, mix gently, and pour into Petri dishes

Test Procedure

1. Streak suspect colonies from selective media (e.g., Oxford or PALCAM agar)
2. Incubate at 37°C for 18–24 hours under aerobic conditions
3. Observe colony morphology

Interpretation of Results

• Colonies typically appear:
  • 1–2 mm in diameter
  • Convex, colorless, and opaque
  • Entire edges
  • Bluish appearance under oblique light with granular surface

Further confirmatory tests are recommended for definitive identification.

Quality Control

• Tested with:
  • Listeria monocytogenes 4b (WDCM 00021)
  • Listeria monocytogenes 1/2a (WDCM 00109)
• Expected result: Weak to good growth

Storage & Shelf Life

• Dehydrated medium:
  • Store at 10–30°C, dry conditions
  • Shelf life: 4 years
• Prepared plates/bottles:
  • Store at 10–25°C, protected from light
  • Shelf life:
    • Bottles: 2 years
    • Plates: 6 months

Available Formats

Liofilchem™ TSYEA provides a reliable, standardized, and ISO-compliant solution for confirming Listeria isolates. Its balanced formulation ensures consistent growth and clear colony morphology, supporting accurate identification and enumeration in food safety workflows.

The Liofilchem™ Tryptone Soy Yeast Extract Agar (TSYEA) is an essential medium for laboratories performing Listeria confirmation and enumeration. With proven performance, compliance with international standards, and flexible formats, it enables accurate, efficient, and regulatory-compliant microbiological testing.