LAURYL SULPHATE BROTH is usedfor the detection and enumeration of coliform bacteria in water, and food products. Lauryl sulphate broth promotes a rich growth and copious gas production from small inocula of coliform organisms. Aerobic sporing bacteria are completely inhibited. Tryptone provides the nitrogen, carbon compounds, vitamins and amino acids. Lactose is the fermentable sugar. Sodium chloride maintains the osmotic balance of the medium. Dipotassium phosphate and Mono potassium phosphate controls the pH during fermentation of Lactose. Lactose-positive bacteria metabolize lactose with gas formation is indicated by using inverted Durham tubes. Incubate at the wished temperature for 18-24 hours. In case of gas formation the Durham tubes rise or/and show bubbles. Turbidity of the medium accompanied by formation of gas within 48 hours is a positive presumptive test for the presence of E. coli and/or other coliform organisms. Prepared Broth becomes cloudy if stored at 2-8°C, but it should get cleared at room temperature. If there is fermentation in the tube incubated at 44°C after 8 to 24 hours, perform indole test by adding Kovac‘s reagent (TR 008). A positive indole test in a broth tube showing gas production at 44°C indicates the presence of Escherichia coli. If no fermentation occurs in the tube incubated at 37°C after 24 hours, the primary fermentation is assumed to be due to organisms other than coliforms.