EWING MALONATE BROTH MODIFIED 500 grams/bottle

Ewing Malonate Broth Modified is prepared following Leifsons formula and modified with the addition of yeast extract and dextrose, for the differentiation of coliforms and other enteric organisms. It is widely used for the differentiation of Enterobacter and Escherichia coli based on the use of malonate. Examples of microorganisms with positive malonate activity are Enterobacter, Klebsiella and strains of Arizona. Some examples of those not able to use malonate are Escherichia, Salmonella and Serratia, amongst others. Malonate utilization as a carbon source, in conjunction with ammonium sulphate as a nitrogen source during growth, produces sodium hydroxide and thereby increased alkalinity, which changes the color of the medium from green to blue due to the pH indicator bromothymol blue. Yeast extract is a source of vitamins, particularly of the B-group essential for bacterial growth. Dextrose is the fermentable carbohydrate providing carbon and energy. Potassium phosphates act as a buffer system. Sodium chloride supplies essential electrolytes for transport and osmotic balance. The organisms that do not utilize malonate do not produce a color change and the medium remains the original green color. Some malonate-negative strains produce a yellow color due to the fermentation of dextrose, which increases acidity, and the medium turns yellow at a pH of 6,0.