MacConkey Broth with Neutral Red, 2.5 kg (C08-0445-475)

MacConkey Broth is widely used as a differential medium for detection and enumeration of coliforms from a wide variety of clinical, food and water samples. Identification is based on colour change of the medium due to the indicator neutral red used (1, 2). Peptic digest of animal tissue provides necessary nitrogen source. Lactose serves as the fermentable carbohydrate source. Sodium chloride maintains the osmotic balance of the cells. The selective action of these media is attributed to the presence of bile salts, which are inhibitory to most species of gram-positive bacteria. Gram-negative bacteria usually grow well on these media and are differentiated by their ability to ferment lactose. The colour change of the medium shown by lactose-fermenters is due to production of acid from lactose and a subsequent colour change of the indicator dye when the pH of the media falls below 6.8. Lactose non-fermenting strains, such as Shigella and Salmonella do not alter the appearance of the medium. The medium turns pink in case of lactose fermenters and yellow in case of non- lactose-fermenters, due to neutral red. MacConkey Broth , which contains neutral red as an indicator is considered as a standard medium for the primary isolation as well as presumptive identification of coliform-aerogenes group of organisms in food and water. 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.MacConkey A. T., 1900, The Lancet, ii: 20. 2.MacConkey A. T., 1905, J. Hyg. 5: 333