Liofilchem® Chromatic™ Coli Coliform

Liofilchem® Chromatic™ Coli Coliform is a chromogenic selective medium formulated for the detection and enumeration of β-glucuronidase-positive Escherichia coli and coliform bacteria in food, water, and environmental samples.

This medium provides rapid and reliable identification of E. coli and other coliforms through distinct chromogenic reactions based on colony color and morphology. It complies with international standards for food safety microbiology and water quality testing, offering laboratories an accurate and efficient solution for microbial enumeration in compliance with ISO 4832, ISO 9308-1, and EN 15721 guidelines.

Key Features

• Chromogenic differentiation of E. coli and coliforms by enzyme-specific color reactions.
• Supports direct inoculation, spread plating, pour plating, or membrane filtration techniques.
• RODAC plate format available for surface monitoring.
• Distinct colony colors: E. coli (green), coliforms (mauve), others (colorless).
• No autoclaving required, preserving chromogenic substrate activity.
• ISO and APHA compliant for food and water microbiology.
• Rapid results within 18–24 hours.

Typical Formula (per litre)

Principle of the Method

• Peptone and yeast extract supply essential nutrients for bacterial growth.
• Sodium chloride maintains osmotic balance.
• The chromogenic substrate system differentiates E. coli (β-glucuronidase positive) from other coliforms based on color reactions.
• Selective agents inhibit Gram-positive organisms, allowing only Gram-negative enteric bacteria to grow.
• Agar solidifies the medium for colony visualization and counting.

Preparation

Dehydrated Medium

1. Suspend 39.7 g of powder in 1 L of distilled or deionized water.
2. Heat to boil while mixing until completely dissolved.
3. Do not autoclave.

Medium in Bottles

1. Loosen cap and melt in a 100°C water bath until fully dissolved.
2. Mix gently to ensure homogeneity, avoiding foaming.
3. Cool to 45–50°C and aseptically pour into Petri dishes.

Test Procedure

• Inoculate solid samples directly by streaking.
• For liquid samples, use spread plating, pour plating, or membrane filtration.
• For surface sampling, use RODAC plates.
• Incubate aerobically at 35 ± 2°C for 18–24 hours.
• Alternative incubation:
  • 44 ± 1°C for 24 hours (fecal coliform detection).
  • 30 ± 1°C for 24–48 hours (total coliform enumeration).

Interpretation of Results

Quality Control

Incubation: 35 ± 2°C for 18–24 hours (aerobic).

Appearance (Dehydrated): light beige, free-flowing powder.

Appearance (Prepared): slightly opalescent, light amber.

Storage and Stability

• Store dehydrated medium at 10–30°C, dry and tightly sealed.
• Store bottled media and plates at 2–8°C, protected from light.
• Shelf life:
  • Dehydrated medium – 2 years
  • Bottled medium – 1 year
  • Ready-to-use plates – 4 months

Safety and Handling

• For in vitro diagnostic use only.
• Use by trained microbiology personnel.
• Handle as per standard biosafety practices.
• Dispose of contaminated materials per local and institutional regulations.

Ordering Information

Liofilchem® Chromatic™ Coli Coliform provides a rapid, reliable, and efficient chromogenic medium for the detection and enumeration of Escherichia coli and other coliforms in food, water, and environmental samples. Its distinct color differentiation, compliance with ISO 10272 and APHA methods, and flexible formats make it ideal for food safety, water quality, and public health laboratories requiring fast, accurate microbial enumeration.