Dichloran Medium Base with Rose Bengal, 500 g

Dichloran Medium Base with Rose Bengal is formulated as described by King et al (1), which is a modification of Rose Bengal Chloramphenicol Agar (2). Dichloran Medium Base with Rose Bengal is used along with Rose Bengal Chloramphenicol Agar where it is necessary to enumerate yeasts in the presence of molds. Peptic digest of animal tissue provides nitrogen, vitamins and minerals. Dextrose is a carbohydrate source. Phosphate buffers the medium. Magnesium sulfate provides divalent cations and sulfate. Dichloran is an antifungal agent, added to the medium to reduce colony diameters of spreading fungi. Rose bengal exhibits an improved inhibitory activity at pH 5.6 and therefore the final pH of the medium is reduced to 5.6 for the inhibition of spreading fungi (1). The presence of rose bengal in the medium suppresses the growth of bacteria and restricts the size and height of colonies of the more rapidly growing molds. The concentration of rose bengal is reduced for optimal performance with dichloran. dditionally, rose bengal is taken up by yeast and mold colonies, which allows these colonies to be easily recognized and enumerated. Add 40 ml of food sample to 200 ml of 0.1% Peptone water (M028) and shake periodically for 30 minutes (3) or process in stomacher for 30 seconds (4). Inoculate 0.1 ml of this sample on Dichloran Medium Base with Rose Bengal. Report the number of colonies per gram of food. 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. King D.A. Jr., Hocking A.D. and Pitt J.I., 1979, J. Appl. Environ. Microbiol., 37:959. 2. Jarvis B., 1973, J. Appl. Bact., 36:723. 3. Sharf J.M. (Ed.), 1966, American Public Health Association, 2nd ed., New York. 4. Sharp A.N. and Jackson A.K., 1972, J. Appl. Bact., 24:175.