FEATURES

DESCRIPTIONS

Ma cc on key agar is the earliest selective and differential medium for cultivation of coliform organisms (1, 2). subsequently MA cc on key agar and Broth have been recommended for use in microbiological examination of foodstuffs (3) and for direct plating/inoculation of water samples for coliform Counts (4). this medium is also accepted by the standard methods for the examination of Milk and dairy products (5). British Pharmacopoeia (6) has recommended this medium for the subculture and identification of Escherichia coli . It is also cited as agar medium H. It is also recommended by and in accordance with the harmonized method of USP/BP/EP/JP (7, 6, 8, 9). pancreatic digest of gelatin and peptones (meat and casein) provide the essential nutrients, vitamins and nitrogenous factors required for growth of microorganisms. Lactose monohydrate is the fermentable source of carbohydrate. The selective action of this medium is attributed to crystal violet and bile salts, which are inhibitory to most species of gram-positive bacteria. Sodium Chloride maintains the osmotic balance in the medium. After enrichment of Escherichia coli in MA cc on key Broth (M083B), it is then sub cultured on MA cc on key agar. Gram-negative bacteria usually grow well on the medium and are differentiated by their ability to ferment lactose. Lactose fermenting strains grow as red or pink and may be surrounded by a zone of acid precipitated bile. The red color is due to production of acid from lactose, absorption of neutral red and a subsequent color change of the dye when the pH of medium falls below 6.8. Lactose non-fermenting strains, such as Shigella and Salmonella are colorless and transparent and typically do not alter appearance of the medium. Yersinia enterocolitica may appear as small, non-lactose fermenting colonies after incubation at room temperature. Directions: suspend 49.53 grams of Dehydrated medium in 1000 ml purified/distilled water.