M-EMB Broth, 5 kg

The membrane filter technique is extremely useful in monitoring water samples. As related to the membrane filter technique, the coliform group is defined as those facultative anaerobic, gram-negative, non-spore-forming, rod-shaped bacteria that develop red colonies with a metallic sheen within 24 hours at 35-37°C on an Endo-type medium containing lactose (1). M-EMB Broth is a selective differential medium used for the detection of members of the coliform group by membrane filtration. M-EMB Broth is formulated as per Clark et al (2). Proteose peptone and yeast extract serve as sources of carbonaceous and nitrogenous growth nutrients. Lactose is the fermentable carbohydrate and energy source. Bile salts mixture helps to inhibit the accompanying non-coliforms. Sodium chloride maintains the osmotic equilibrium of the medium while dipotassium phosphate buffers the medium. Eosin-Y and methylene blue serve as the indicator system in the medium. The two dyes combine to form a precipitate at acidic pH, due to lactose fermentation. Eosin Y also serves as an inhibitor (3). Membrane filters through which the test water sample has been passed are initially enriched for 2 hours by incubating the filter on M-Enrichment Broth (M1109). These enriched cultures (filters) are then transferred onto sterile absorbent cotton pads saturated with 2 ml of M-EMB Broth (M1105). Incubation is done at 35-37°C for 18-24 hours. Lactose fermenting coliforms produce pink coloured colonies while non-lactose fermenting coliforms will form colorless colonies. Storage and Shelf-life: Store below 30°C in tightly closed container and the prepared medium at 2-8°C. Use before expiry date on the label. References: 1. Eaton A. D., Clesceri L. S. and Greenberg A. E., (Eds.), 1998, Standard Methods for the Examination of water and Waste water, 20th Ed., American Public Health Association, Washington, D.C. 2. Clark H. F., Geldreich E. E., Jeter M. L. and Kabler P. W., Public Health Rep., 66, 951 3. MacFaddin J. F., 1985, Media for Isolation-Cultivation-Identification-Maintenance of Medical Bacteria, Vol. 1, Williams and Wilkins, Baltimore.