Red Bile Agar Research Paper

566 Words 3 Pages
Violet red bile agar is a selective medium used to identify lactose-fermenting coliforms. This medium is typically used to test dairy products and water. The medium contains lactose which acts as a carbohydrate source, bile salts and crystal violet that act as an inhibitory agent towards gram-positive microorganisms and neutral red is added to serve as a pH indicator, microorganisms lower the pH which results in the colonies turning red.
Some of the organisms that grow on this medium are: Escherichia coli ,Enterobacter aerogenes and Enterococcus.Lactose-fermenting organisms appear as pink or red colonies , E.coli appear pink or red, E.aerogenes appear pink in colour ,Enterococcus appear rose in colour and the colour are pin point in size
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B-complex which is formed by pyruvate yeast extract encourages growth. The selectivity of the medium is influenced by Lithium chloride and 1% potassium Tellurite solution which inhibits the growth of other organisms beside staphylococci. Coagulase differentiation results from the addition of potassium Tellurite and egg yolk emulsion. Staphylococci that has lectithinase breaks down the egg yolk and causes hemolysis around the colonies. After an incubation time of 24 hours the colonies appeared black, this occurred as a result of potassium Tellurite being reduced. From the results it can also be said that this particular strain is coagulase-positive as hemolysis was present. Boils, impetigo, food poisoning, cellulitis, and toxic shock syndrome are some of the effects of Staphylococcus aureus.
Salmonella Shigella Agar is used for the isolation of Salmonella spp. and some strains of Shigella spp (neogen). Beef extract, enzymatic digest of casein and animal tissue provide suitable sources of nitrogen, carbon and vitamin required for growth. Lactose is present as a carbohydrate source. Bile salts, sodium citrate and brilliant green inhibits gram-positive bacteria. Neutral red is the pH

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