Liofilchem® Chromocult E. Coli/Coliform Agar, 500G

Chromatic™ Coli Coliform is a selective chromogenic culture medium designed for the simultaneous detection and enumeration of Escherichia coli and coliform bacteria in food, water, and environmental samples. It enables rapid differentiation of E. coli and coliform bacteria through distinct colony coloration, making it suitable for microbiological analysis in both clinical and industrial applications.

Key Features

1. Chromogenic Properties:
   • Differentiates E. coli (β-glucuronidase-positive strains) from other coliform bacteria and non-coliform species.
   • Enables direct visual identification based on colony color:
     • E. coli: Green colonies.
     • Other coliforms (e.g., Klebsiella pneumoniae, Enterobacter cloacae): Mauve colonies.
     • Non-coliform bacteria: Colorless colonies.
2. Application:
   • Detection and enumeration of E. coli and coliforms in food and water samples.
   • Ideal for routine microbiological testing in food safety, water quality monitoring, and environmental hygiene assessment.
3. Pharmacopoeial Compliance:
   • Conforms to recognized international standards for microbiological testing.

Composition

• Peptone (15.0 g/l): Provides essential amino acids, nitrogen, and carbon for microbial growth.
• Yeast Extract (3.0 g/l): Supplies B-group vitamins and enhances microbial metabolism.
• Sodium Chloride (5.0 g/l): Maintains osmotic balance.
• Chromogenic and Selective Mix (1.7 g/l):
  • Differentiates bacterial species based on enzymatic activity.
  • Inhibits Gram-positive organisms.
• Agar (15.0 g/l): Solidifying agent.
• Final pH: 7.2 ± 0.2 at 25°C.

Preparation

1. Dehydrated Medium:
   • Suspend 39.7 g of powder in 1 liter of distilled or deionized water.
   • Heat to boiling while stirring frequently until completely dissolved.
   • Do not autoclave.
   • Cool the medium to 45-50°C before pouring into Petri dishes.
2. Pre-prepared Bottles:
   • Melt in a water bath at 100°C with the cap loosened.
   • Mix to ensure homogeneity and cool to 45-50°C.
   • Pour aseptically into sterile Petri dishes.

Test Procedure

1. Sample Inoculation:
   • Solid Samples: Streak directly on the surface of the medium.
   • Liquid Samples:
     • Use spread plating, pour plating, or membrane filtration methods.
   • Surface Sampling: Utilize RODAC plates by pressing them against the test area.
2. Incubation:
   • Aerobically incubate at 35 ± 2°C for 18-24 hours.
   • Incubation conditions may vary:
     • 44 ± 1°C for 24 hours for fecal coliform bacteria detection.
     • 30 ± 1°C for 24-48 hours to maximize total coliform detection.

Result Interpretation

• Typical Colony Appearance:
  • E. coli: Green colonies (β-glucuronidase-positive).
  • Other coliforms (e.g., Klebsiella pneumoniae, Enterobacter cloacae): Mauve colonies.
  • Non-coliform bacteria (e.g., Proteus mirabilis, Pseudomonas aeruginosa): Colorless colonies.
  • Note: β-glucuronidase-negative E. coli strains (e.g., E. coli O157) appear colorless.

Quality Control

• Inoculum for Productivity: 50-100 CFU.
• Inoculum for Selectivity: 10⁴–10⁶ CFU.
• Incubation Conditions: 35 ± 2°C for 18-24 hours.
• Expected Outcomes:
  • Escherichia coli ATCC® 25922: Good growth; green colonies.
  • Klebsiella pneumoniae ATCC® 13883: Good growth; mauve colonies.
  • Proteus mirabilis ATCC® 25923: Good growth; colorless colonies.
  • Staphylococcus aureus ATCC® 25923: Partially to completely inhibited.

Appearance

1. Dehydrated Medium:
   • Free-flowing, homogeneous, light beige powder.
2. Prepared Medium:
   • Slightly opalescent, light amber gel.

Storage and Shelf Life

1. Dehydrated Medium:
   • Store at 10-30°C in a dry environment in its original tightly closed container.
   • Shelf life: 2 years.
2. Pre-prepared Bottles:
   • Store at 2-8°C, away from light.
   • Shelf life: 1 year.
3. Ready-to-Use Plates:
   • Store at 2-8°C, away from light.
   • Shelf life: 4 months.

Precautions

1. The product does not contain hazardous substances in concentrations exceeding current legislative limits.
2. Designed for professional use only; must be handled by trained personnel in laboratory conditions.
3. Consult the Safety Data Sheet (SDS) for details on safe handling and disposal.
4. Dispose of waste in accordance with national and local regulations.

Advantages

• Efficient and Rapid: Detects and differentiates E. coli and coliforms within 24 hours.
• Chromogenic Identification: Provides clear, distinct colony colors for easy identification.
• Selective: Effectively inhibits Gram-positive bacteria to reduce false positives.
• Compliant: Conforms to international microbiological testing standards.

Ordering Information

• Dehydrated Media:
  • 100 g (Ref. 620610)
  • 500 g (Ref. 610610)
• Ready-to-Use Plates:
  • 90 mm plates (Ref. 11613)
  • 60 mm plates (Ref. 163702)
  • RODAC plates (Ref. 15344)
• Pre-prepared Bottles:
  • 6 x 100 ml bottles (Ref. 481120)

Liofilchem® Chromatic™ Coli Coliform medium offers a highly selective, efficient, and visually intuitive method for the detection and enumeration of E. coli and coliform bacteria. Its chromogenic properties ensure accurate differentiation and compliance with rigorous microbiological testing standards, making it indispensable in food safety, water quality testing, and environmental monitoring.