Dextrose Agar

Potato Dextrose Agar (PDA) is used for the cultivation of fungi. Potato Dextrose Agar (PDA) is a general purpose medium for yeasts and molds that can be supplemented with acid or antibiotics to inhibit bacterial growth. It is recommended for plate count methods for foods, dairy products and testing cosmetics. PDA can be used for growing clinically significant yeast and molds. The nutritionally rich base (potato infusion) encourages mold sporulation and pigment production in some dermatophytes.

Principle of Potato Dextrose Agar (PDA)

Potato Dextrose Agar is composed of dehydrated Potato Infusion and Dextrose that encourage luxuriant fungal growth. Agar is added as the solidifying agent. Many standard procedures use a specified amount of sterile tartaric acid (10%) to lower the pH of this medium to 3.5 +/- 0.1, inhibiting bacterial growth. Chloramphenicol acts as a selective agent to inhibit bacterial overgrowth of competing microorganisms from mixed specimens, while permitting the selective isolation of fungi.

Note: Do not reheat the acidified medium, heating in the acid state will hydrolyze the agar.

Uses of Potato Dextrose Agar (PDA)

• Potato Dextrose Agar is used for the detection of yeasts and molds in dairy products and prepared foods.
• It may also be used for the cultivation of yeasts and molds from clinical specimens.
• Potato Dextrose Agar with TA (Tartaric Acid) is recommended for the microbial examination of food and dairy products.
• Potato Dextrose Agar with Chlortetracycline is recommended for the microbial enumeration of yeast and mold from cosmetics.
• Potato Dextrose Agar with Chloramphenicol is recommended for the selective cultivation of fungi from mixed samples.