Fraser Secondary Enrich Broth Base, 500G g

Fraser Secondary Enrichment Broth is a modification of United States Department of Agriculture-Food Safety Inspection Service (USDA-FSIS) UVM Secondary Enrichment Broth. It is based on the formulation of Fraser and Sperber (1) and found to be remarkably accurate in detecting Listeria species in food and environmental samples (2). Fraser Secondary Enrichment Broth is recommended by APHA (3). Fraser Secondary Enrichment Broth Base is formulated so as to provide optimum conditions for the growth of Listeria . Proteose peptone, casein enzymic hydrolysate, yeast extract, and beef extract make the media highly nutritive by providing essential nutrients including carbonaceous and nitrogenous substances. Phosphates maintain the buffering capacity of the medium. All Listeria species exhibit beta-glucosidase activity which is evident by the blackening of the media. Listeria species hydrolyze esculin (substituted glucoside) to glucose and esculetin. The latter combines with ferric ions of ferric ammonium citrate, resulting in the formation of 6-7 dihydroxycoumarin, a black brown complex. Ferric ammonium citrate also enhances the growth of L. monocytogenes (4). The high salt tolerance (of sodium chloride) of Listeria is used as means to inhibit the growth of Enterococci. Lithium chloride is also used to inhibit Enterococci, which also possess the ability to hydrolyze esculin. Growth of accompanying bacteria is largely inhibited by the addition of Nalidixic acid and Acriflavin hydrochloride (FD). 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. Fraser J.A. and Sperber W.H., 1988, Food Protect., 51(10):762. 2. McClain D. and Lee W.H., 1988, J. Assoc. Off. Anal. Chem., 71(3):660. 3. Downes F. P. and Ito K., (Eds.), 2001, Compendium of Methods for the Microbiological Examination of Foods, 4th Ed., APHA, Washington, D.C. 4. Cowart R. E. and Foster B. G., 1985, J. Infect. Dis.; 151:172.