Most Probable Number (MPN) Test: Principle, Procedure, Results
Purpose: To enumerate the number of bacteria present in the water by the MPN method. To identify the bacteria present in the drinking water sample. Principle: Water to be tested is diluted serially and inoculated in lactose broth, coliforms if present in water utilizes the lactose present in the medium to produce acid and gas. The presence of acid is indicated by the color change of the medium and the presence of gas is detected as gas bubbles collected in the inverted Durham tube present in the medium. The number of total coliforms is determined by counting the number of tubes giving positive reaction (i.e both color change and gas production) and comparing the pattern of positive results (the number of tubes showing growth at each dilution) with standard statistical tables. Type of container and additives Sterile container Requirements: Equipment: Test tubes, Durham tube, sterile plates, laminar airflow, Incubator. Reagents/ Media: MacConkey broth, Stains, B...