Rose Bengal Agar + Chloramphenicol

Bacteriological peptone provides the nitrogen, vitamins, minerals and amino acids source. Dextrose is the fermentable carbohydrate as a carbon and energy source. Potassium phosphate is the buffer. Magnesium sulfate provides sulfur and other trace elements. Rose bengal is a selective agent that inhibits the growth of bacteria and limits the size and height of faster-growing molds, allowing for the development and detection of other slower-growing yeasts and molds, which appear pink colored. Chloramphenicol serves as a selective agent, inhibiting bacterial growth. It is a recommended antibiotic for neutral media due to its heat stability and wide bacterial spectrum. Bacteriological agar is the solidifying agent.

Preparation

Suspend 31.6 grams of the medium in one liter of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Sterilize in autoclave at 121 °C for 15 minutes. Cool to 45-50 °C, mix well and dispense into plates.

Instructions for use

1. The inoculation can be carried out from a diluted source, either by spreading 0.1 mL of each dilution onto the prepared plates, or by the pouring method, depositing 1 mL of each dilution into the empty plate and pouring the medium immediately after (once it has been cooled to 45 °C).
2. Incubate for 7 days at 25-30 °C.

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• Marshall, R.T. (ed) 1993. Standard methods for the examination of dairy products, 16th ed. American Public Health Assoc., Washington, DC.