For enumeration of Escherichia coli in water by membrane filter technique. M-LAURYL SULPHATE BROTHis used for enumeration of Escherichia coli in water by membrane filter technique. Scientist ‘Burman’substituted Teepol in place of bile salts in the Membrane Enriched Teepol Broth, a membrane filtration test medium used to detect coliform organisms in water. The replacement of bile salts by Teepol was previously mentioned by other microbiology groups. Membrane LaurylSulphate Broth is similar to Membrane Enriched Teepol Broth except that the selective agent Teepol has been replaced by 0.1% (w/v) sodium lauryl sulphate. Peptic digest of animal tissue and Yeast extract provide carbon, nitrogen, amino acids, minerals, vitamins, trace elements and other essential nutrients for growth. Lactose serves asa fermentable carbohydrate source.Phenol red is the indicator and change from red to yellow because of the acid production from the fermentation. Sodium lauryl sulphate inhibits grampositive organisms. Mix the brothand pour the contents evenly over theabsorbent pad and place the lidon the Petri plates.Filter sample or diluted sampleusing a 47mm white gridded0.45 μm membrane filter, gridside up. Transfer the filter to thepreviously prepared Petri platesusingsterile forceps. Place the filter grid side up, ontothe absorbent pad with a slightrolling motion. Check for trappedair under the filter and make surethe filter touches the entire pad.Replace the Petri plate’slid. Invert the Petri platesand incubateat 35°C and at 440Cfor 24 hours.Yellow colour colonies are formed for the confirmation of E.coli. Count the colonies. Use a10 to 15X microscopeif necessary.