Glucose Chloramphenicol Agar

Yeast extract is the water-soluble portion of hydrolyzed yeast and is a source of vitamins, particularly of the B-group, and other growth nutrients that stimulate yeast and mold development. Glucose is the fermentable carbohydrate as a carbon and energy source. Chloramphenicol is an antibiotic which aids in isolating pathogenic fungi from heavily contaminated material, as it inhibits most contaminating bacteria. It is a recommended antibiotic for use with media due to its heat stability and wide bacterial spectrum. Bacteriological agar is the solidifying agent.

Preparation

Suspend 40.2 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 50 °C, mix well and dispense into plates.

Instructions for use

Inoculation method:

1. Transfer to an empty Petri dish 1 mL of the test sample, if liquid, or 1 mL of the initial suspension in the case of other products.
2. Prepare dilutions if needed.
3. Pour about 15 mL of Glucose Chloramphenicol Agar medium, previously melted and maintained at 45 °C in the water bath, into each Petri dish.
4. Carefully mix the inoculum with the medium by rotating the Petri dish and allow the mixture to solidify. The time taken between the preparation of the first dilution and the mixing of the inoculum with the medium shall not exceed 15 min.
5. Incubate the dishes in an inverted position at 25 °C for 5 days.

• FIL-IDF (1991) Standard 94B. Enumeration of yeast and moulds. Colony Count Technique at 25 °C.
• ISO (1981) ISO/DIS 6611: Milk and Milk products: Enumeration of yeast and moulds colony count technique at 25 °C.
• DIN Standard 10186. Mikrobiologische Milchuntersuchung. Bestimmung der Anzahl von Hefen und Schimmelpilzen.