Liofilchem® Tergitol Agar Base

Tergitol Agar Base is a specialized microbiological medium designed for the selective isolation, detection, and enumeration of Escherichia coli and coliform bacteria in water samples, following the ISO 9308-1 guidelines. This medium is essential for water quality testing, particularly in public health, food safety, and environmental monitoring.

Key Features

• ISO 9308-1 Compliance: Recommended for use in detecting E. coli and coliforms through membrane filtration techniques.
• Selective Growth: Incorporates Tergitol 7 (sodium heptadecylsulfate) and triphenyltetrazolium chloride (TTC) to suppress Gram-positive bacteria and enhance coliform recovery.
• Colony Differentiation: Produces distinct colony colors for easy identification:
  • E. coli: Yellow-orange colonies on a yellow medium.
  • Enterobacter/Klebsiella: Yellow colonies on a yellow medium.
  • Salmonella/Shigella/Proteus/Pseudomonas: Dark red colonies on a green medium.
• Dehydrated Medium: Convenient for storage and preparation, ensuring a long shelf life and consistent performance.

Composition (Per Liter)

• Lactose: 20.0 g (fermentable carbohydrate source)
• Peptone: 10.0 g (nitrogen and amino acid source)
• Yeast Extract: 6.0 g (B-group vitamin enrichment)
• Meat Extract: 5.0 g (additional nutrients and growth factors)
• Bromothymol Blue: 0.05 g (pH indicator)
• Agar: 15.0 g (solidifying agent)
• Final pH: 7.2 ± 0.1 at 25°C.

Preparation Instructions

1. Reconstitution: Suspend 56.0 g of dehydrated medium in 1 liter of distilled or deionized water.
2. Dissolution: Heat to boiling while stirring gently until the powder is fully dissolved.
3. Sterilization: Autoclave at 121°C for 15 minutes.
4. Supplementation:
   • Cool to 45-50°C.
   • Aseptically add 2.5 ml of TTC 1% Supplement (ref. 80300).
   • Add 7 ml of Tergitol 1.5% Supplement (provided in the package).
   • Mix thoroughly.
5. Dispensing: Pour into Petri dishes and allow to solidify.

Testing Procedure

Membrane Filtration Method:

1. Sample Filtration:
   • Filter two 100 ml water samples through sterile membranes.
2. Membrane Transfer:
   • Place each membrane onto the prepared Tergitol Agar Base plates.
3. Incubation:
   • Plate 1: Incubate at 37°C for 24 hours (for total coliforms).
   • Plate 2: Incubate at 44°C for 16-24 hours (for E. coli).
4. Colony Observation:
   • Identify colony color and medium color for results.

Interpretation of Results

• E. coli: Yellow-orange colonies on yellow medium.
• Enterobacter/Klebsiella: Yellow colonies on yellow medium.
• Salmonella/Shigella/Proteus/Pseudomonas: Dark red colonies on green medium.

Storage

• Dehydrated Medium:
  • Store at 10-30°C in a dry environment within its original, tightly closed container.
  • Protect from moisture and contamination.
• Prepared Plates:
  • Store at 2-8°C away from direct light.
  • Use before the expiration date on the label.

Quality Control

Dehydrated Medium:

• Appearance: Free-flowing, homogeneous powder with a beige or slightly greenish tint.

Prepared Medium:

• Appearance: Slightly opalescent, green-colored gel without precipitates.

Performance Tests:

• Inoculum Size:
  • Productivity: 10-100 CFU/ml.
  • Selectivity: 10⁴-10⁵ CFU/ml.
  • Specificity: ≤10⁴ CFU/ml.
• Incubation Conditions: 18-24 hours at 35 ± 2°C.
• Expected Results:
  • E. coli (ATCC® 25922): Good growth, yellow-orange colonies.
  • Salmonella typhimurium (ATCC® 14028): Good growth, dark red colonies.
  • Enterococcus faecalis (ATCC® 29212): Inhibited.

Safety Precautions

• For professional use in laboratory settings.
• Operators should be trained in microbiological techniques.
• Handle according to safety protocols to avoid cross-contamination.
• Consult the Safety Data Sheet (SDS) for additional handling instructions.

Shelf Life

• Dehydrated medium: 4 years.
• Prepared plates: 6 months.

Packaging

1. 610184: 500 g powder + 2 x 40 ml Tergitol 1.5% Supplement.
2. 620184: 100 g powder + 1 x 25 ml Tergitol 1.5% Supplement.

Applications

• Water Testing:
  • Detect and enumerate E. coli and coliform bacteria in drinking water, recreational water, and wastewater.
• Food Safety:
  • Monitor bacterial contamination in food and beverages.
• Environmental Monitoring:
  • Assess waterborne pathogens in industrial and agricultural settings.

References

1. ISO 9308-1:2000 – Detection and enumeration of E. coli and coliform bacteria by membrane filtration.
2. Chapman, G.H. (1947). J. Bact. 53: 504.
3. Sambrook et al. (1989). Molecular cloning: A laboratory manual, 2nd ed.
4. Tartoff, K.D., and Hobbs, C.A. (1987). Bethesda Research Laboratories Focus. 9:12.

Liofilchem® Tergitol Agar Base offers a robust and reliable solution for microbiological detection and enumeration of coliforms, aligning with industry standards for water quality and public health.