M-E.coli Medium (without Membrane Filter)

Principle And Interpretation

DriFilter Membrane Nutrient Pad Medium is ready to use sterile culture media in the form of a 50 mm biological inert absorbent pads impregnated with Sabouraud Dextrose Medium, then dried and sterilized in 55 mm petri plate. They eliminate the need of laborious media preparation and autoclaving procedures. The nutrient pads are to be just rewetted with sterile distilled water and are ready to use. Use of nutrient pads allows larger sample volumes to be tested at a time. Interpretation of results is directly by counting the CFUs and also quantifies the microbial load present in the sample.

M-E.coli Medium is used for detection and differentiation of Escherichia coli and coliforms in water samples using membrane filter technique. It is based on Tryptone Bile Agar used for detection of Escherichia coli in foods (1) where recovery of Escherichia coli is faster, more reliable and accurate.

The water sample is filtered through membranes and then placed on pad saturated with M-E.coli Broth and incubated at 37°C in sealed Petri plates. The medium contains chromogenic mixture, which helps to detect glucuronidase activity of Escherichia coli (3). This specific enzyme differentiates Escherichia coli from other coliforms. Escherichia coli cells split the chromogenic mixture with the help of glucuronidase to give blue colouration to the colonies. Coliforms other than Escherichia coli turn red as they reduce TTC (2,3,5-triphenyl tetrazolium chloride). Thus, the resulting colour distinction allows simple interpretation of test without further confirmation. tryptone provides the essential growth nutrients to the organisms. Bile salts inhibit gram - positive organisms.