Dextrose Agar, 500 g

Dextrose in culture media serves as a source of energy. A basal media with 0.5 - 1.0% dextrose, supplemented with defibrinated blood is recommended for the isolation of a wide variety of fastidious organisms (1). Dextrose Agar, recommended by APHA (2), contains 1.0% dextrose and therefore supports early and luxuriant growth of a variety of organisms including older cultures. The lag phase is comparatively reduced on this medium. But due to high concentrations of dextrose, the medium is not recommended for studying the haemolytic pattern of organism since dextrose interferes with the haemolytic reaction. Dextrose Agar contains high concentration of dextrose as an energy source for the rapid growth of microorganisms. However this medium is not very suitable for the study of haemolysis because of high carbohydrate content. Beef extract and tryptose serve as sources of nitrogenous compounds, sulphur, carbon, vitamins and minerals. Osmotic balance of the medium is maintained by sodium chloride. 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. Norton, 1932, J. Lab. Clin. Med., 17:585. 2. Vanderzant C. and Splittstoesser D. F. (Eds.), 1992, Compendium of Methods for the Microbiological Examination of Foods, 3rd Ed., APHA, Washington, D.C.