Tergitol Agar Base is a basal medium recommended by ISO 9308-1 for the detection and enumeration of Escherichia coli and coliforms in water using the membrane filtration technique. This product is crucial in environmental and public health laboratories for monitoring water quality.
Composition and Principle
Tergitol Agar Base is composed of Lactose, Peptone, Yeast Extract, Meat Extract, Bromothymol Blue, and Agar. This formulation provides a nutritive base for the growth of E. coli and coliforms. Peptone and meat extract are the sources of nitrogen, carbon, and amino acids, essential for bacterial growth. Yeast extract supplies B-group vitamins, further stimulating bacterial proliferation. Lactose is the fermentable carbohydrate, and Bromothymol Blue serves as an indicator dye, facilitating the identification of lactose-fermenting colonies. Agar is the solidifying agent, and the addition of Sodium heptadecylsulfate (Tergitol 7) inhibits the growth of Gram-positive microorganisms, allowing superior recovery of coliforms.
Preparation and Usage
To prepare the medium, 56.0 g of powder is suspended in 1 liter of deionized or distilled sterile water, heated to boiling until completely dissolved, and then sterilized in an autoclave at 121°C for 15 minutes. After cooling to 45-50°C, 2.5 ml of TTC 1% Supplement and 7 ml of Tergitol 1.5% Supplement are aseptically added, mixed well, and dispensed into Petri dishes.
Technique and Interpretation of Results
The membrane filtration method is used for sample analysis. Two 100 ml aliquots of the water sample are filtered through sterile membranes. Each membrane is then placed on an agar plate, with one plate incubated at 37°C for 24 hours for total coliforms and the other at 44°C for 16-24 hours for E. coli. E. coli forms yellow-orange colonies on a yellow medium, while other Enterobacteriaceae like Enterobacter and Klebsiella produce yellow colonies. Non-target organisms like Salmonella, Shigella, Proteus, and Pseudomonas form dark red colonies on a green medium.
Storage and Precautions
The powder is hygroscopic and should be stored at 10-30°C in a dry environment, in its original container, tightly closed. Prepared plates should be stored at 2-8°C, away from light. Although not classified as hazardous, it is recommended to consult the safety data sheet for its correct use. The product is intended for professional use and must be used only by properly trained operators.
Tergitol Agar Base is a scientifically formulated medium essential for the accurate detection and enumeration of E. coli and coliforms in water samples. Its selective composition, ease of preparation, and clear interpretative criteria make it a reliable tool for water quality testing in environmental and public health laboratories.