PDA- Composition, Principle, Preparation, Results, Uses


Potato dextrose agar (PDA) is a type of culture medium that is used to grow fungi, such as yeasts and molds. A culture medium is a substance that provides nutrients and other conditions for microorganisms to grow and multiply. PDA is made from potato infusion and dextrose (a form of sugar) that provide carbohydrates and other essential elements for fungal growth. Agar is added as a solidifying agent to make the medium gel-like.

PDA is widely used in microbiology, food science, and clinical laboratories for various purposes. Some of the common uses of PDA are:

  • To isolate and identify fungi from different sources, such as food, dairy products, soil, water, air, and clinical specimens.
  • To count the number of fungal colonies in a sample, which indicates the level of fungal contamination or spoilage.
  • To maintain and preserve fungal cultures for long-term storage or further studies.
  • To test the susceptibility of fungi to different antifungal agents or environmental factors.

PDA is a general-purpose medium that can support the growth of most fungi. However, some fungi may require special additives or modifications to the medium to enhance their growth or selectivity. For example, tartaric acid can be added to lower the pH of the medium and inhibit bacterial growth. Antibiotics like chloramphenicol, chlortetracycline, or cycloheximide can be added to prevent bacterial or saprophytic fungal growth. Some dyes like bromocresol purple or phenol red can be added to indicate the acidity or alkalinity of the medium.

PDA is easy to prepare and use, and it provides a clear contrast between the fungal colonies and the medium. However, PDA also has some limitations, such as:

  • It may not support the growth of some fastidious or slow-growing fungi that require more complex or specific nutrients.
  • It may not differentiate between different types of fungi based on their biochemical or physiological characteristics.
  • It may not prevent the growth of some bacteria or fungi that can tolerate low pH or antibiotics.

Therefore, PDA should be used in combination with other culture media, microscopic examination, biochemical tests, molecular methods, or mass spectrometry for accurate identification and characterization of fungi.