M-Endo Broth MF (MF Endo Medium), 5 kg

It is possible to remove bacteria from fluids by passing them through filters with such small pore size that bacteria are arrested. This filtration technique enables fairly large volumes of water to pass rapidly under pressure, but prevents the passage of any bacteria present. These nutrients are retained on the surface of the membrane which is then brought into contact with suitable liquid nutrients. These diffuse upwards through the pores thereby inducing the organisms to grow as surface colonies which can be counted (1). M-Endo broth is used for the estimation of coliform bacteria in water samples using the membrane filtration technique. Endo Medium was first developed by Endo to differentiate between lactose-fermenters and non-fermenters. This medium employed sodium sulphite and basic fuchsin instead of bile salts to achieve inhibition of gram-positive bacteria (2). M-Endo Broth MF is a selective and differential medium for the detection of coliforms by the membrane filter technique (3). Preliminary enrichment on a non-selective medium is not required in case of M-Endo Broth MF and therefore this is a medium of choice for the determination of coliform bacteria in water and other specimens by one step filtration technique. Casein enzymic hydrolysate, tryptose, peptone special and yeast extract provide essential nutrients especially nitrogenous for the coliforms. Lactose is the fermentable carbohydrate. Sodium sulphite, sodium deoxycholate and basic fuchsin inhibit the growth of gram-positive organisms. Phosphates buffer the medium. Coliforms ferment lactose and the resulting acetaldehyde reacts with sodium sulphite and basic fuchsin to form red colonies and similar colouration of the medium. Lactose nonfermenters form colourless colonies. Storage and Shelf-life: Store below 30°C in tightly closed container and use freshly prepared medium. Use before expiry date on the label. References: 1. Cruickshank R., Duguid J. P., Marmion B. P., Swain R. H. A., (Eds.), Medical Microbiology, 1975, 12th Ed. Vol. II, Churchill Livingstone. 2. Endo S., 1904, Zentralbl. Bakteriol., Abt. 1, Orig.35:109-110. 3. Fifield C. W. and Schaufus C. P., 1958, J. Am. Water Works Assoc. 50:193