Sabouraud Dextrose Agar (SDA) – Composition, Principle, Uses, Preparation and Colony Morphology 4.62/5 (71)

Sabouraud Dextrose Agar (SDA) – Composition, Principle, Uses, Preparation and Colony Morphology

Sabouraud Dextrose Agar (SDA) is used for the isolation, cultivation, and maintenance of non-pathogenic and pathogenic species of fungi and yeasts. SDA was formulated by Sabouraud in 1892 for culturing dermatophytes. The pH is adjusted to approximately 5.6 in order to enhance the growth of fungi, especially dermatophytes, and to slightly inhibit bacterial growth in clinical specimens.

Composition of SDA

Ingredients

In gm/L

Dextrose (Glucose)

40 gm

Peptone

10 gm

Agar

15 gm

Distilled Water

1000 ml

Final pH 5.6 +/- 0.2 at 25ºC.

In addition,

Sabouraud Dextrose Broth is the same formulation as above, without agar added.
Final pH 5.6 +/- 0.2 at 25ºC.
Sabouraud Dextrose Agar with Chloramphenicol contains 50.0 mg of chloramphenicol.
Final pH 5.6 +/- 0.3 at 25ºC.
Sabouraud Dextrose Agar with Chloramphenicol and Gentamicin contains 50.0 mg of chloramphenicol and 5.0 mg gentamicin.
Final pH of 5.6 +/- 0.3 at 25ºC.
Sabouraud Dextrose Agar with Chloramphenicol and Tetracycline contains 50.0 mg of chloramphenicol and 10.0 mg of tetracycline.
Final pH of 5.6 +/- 0.3 at 25ºC.
Sabouraud Dextrose Agar, Emmons has only 20.0 gm of dextrose.
Final pH of 6.9 +/- 0.2 at 25ºC.

Principle of SDA

Peptone (Enzymatic Digest of Casein and Enzymatic Digest of Animal Tissue) provide the nitrogen and vitamin source required for organism growth in SDA. Dextrose is added as the energy and carbon source. Agar is the solidifying agent.

Chloramphenicol and/or tetracycline may be added as broad spectrum antimicrobials to inhibit the growth of a wide range of gram-positive and gram-negative bacteria. Gentamicin is added to further inhibit the growth of gram-negative bacteria.

The neutral pH of the Emmons modification seems to enhance the growth of some pathogenic fungi, such as dermatophytes.

Uses of SDA

  1. SDA is primarily used for the selective cultivation of yeasts, molds and aciduric bacteria.
  2. The medium is often used with antibiotics for the isolation of pathogenic fungi from material containing large numbers of other fungi or bacteria.
  3. This medium is also employed to determine microbial contamination in food, cosmetics, and clinical specimens.

Preparation of SDA

  1. Combine all ingredients in ~900 ml of deioinized water.
  2. Adjust to pH 5.6 with hydrochloric acid and adjust final volume to 1 liter.
  3. Heat to boiling to dissolve the medium completely.
  4. Autoclave at 121ºC for 15 minutes.
  5. Cool to ~45 to 50°C and pour into petri dishes or tubes for slants.

Sabouraud agar plates can be inoculated by streaking, as with standard bacteriological media, or by exposing the medium to ambient air. Typically, molds are incubated at room temperature (22 to 25°C) and yeasts are incubated at 28 to 30°C or 37°C if suspected of being dimorphic fungi. Incubation times will vary, from approximately 2 days for the growth of yeast colonies such as Malasezzia, to 2 to 4 weeks for growth of dermatophytes or dimorphic fungi such as Histoplasma capsulatum. Indeed, the incubation time required to acquire fungal growth is one diagnostic indicator used to identify or confirm fungal species.

Result Interpretation on SDA

Identification of fungi is performed by observing various aspects of colony morphology, characteristic microscopic structures, rate of growth, media which supports the organism’s growth, and source of specimen. Yeasts are identified by various biochemical tests.

Yeasts will grow as creamy to white colonies. Molds will grow as filamentous colonies of various colors.

Colony Morphology on SDA

Colony Morphology on SDA

 

Colony Morphology on SDA

Quality Control of SDA

Appearance
Dehydrated medium: Straw coloured, free-flowing powder.
Prepared medium: Light straw to straw coloured gel.

Positive controls:

Expected results

Candida albicans ATCC® 10231 Good growth; cream colonies
Aspergillus brasiliensis ATCC® 16404 

White mycelium; black spores

Negative control:  
Uninoculated medium No change

Limitations of SDA

  1. Some strains may be encountered that grow poorly or fail to grow on this medium.
  2. Antimicrobial agents added into a medium to inhibit bacteria may also inhibit certain pathogenic fungi.
  3. Avoid overheating a medium with an acidic pH, this may result in a soft medium.
  4. For identification, organisms must be in pure culture.
  5. Morphological, biochemical, and/or serological tests should be performed for final identification.
  6. It does not promote conidiation of filamentous fungi.
Sabouraud Dextrose Agar (SDA) – Composition, Principle, Uses, Preparation and Colony Morphology

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Sabouraud Dextrose Agar (SDA) – Composition, Principle, Uses, Preparation and Colony Morphology

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The Author

Sagar Aryal

I am Sagar Aryal, a passionate Microbiologist and the Scientific Blogger. I did my Master's Degree in Medical Microbiology and currently working as a Lecturer at Department of Microbiology, St. Xavier's College, Kathmandu, Nepal. I am particularly interested in research related to Medical Microbiology and Virology. Find me on Facebook, Twitter or Linkedin !!!

16 Comments

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  1. Good morning please I wish to know how many mg of chloramphenicol antibiotic is added to SDA media to prevent bacteria growth.

    1. add 5mg of chloramphenicol into 500ml SDA media.

  2. How to identify Listeria monocytogen from clinical specimen?

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  4. really interesting, please help my research work in the area of food and industrial microbiology. I will be glad to receive materials in thie regard. I am a masters degree holder in food microbiology, a nigerian.

  5. Hello,

    Can i use Potato Dextrose Agar as alternative to Sabouraud Dextrose Agar?
    Thanks

    1. Hi, i’m helping to give you an answer.

      You could use Potato Dextrose Agar as substitution with addition of bacterial antibiotic (such as chloramphenicol) if you want to cultivate fungi.

      Hope this help.

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  7. Fabolus description (y)

  8. hi,
    dear microbiologist. i am also working in leading pharmaceutical company at qc microbiologist .i want learn research of drug devalpmenet in vaccine

  9. Wonderful….. 🙂 🙂

    1. Thank you 🙂

  10. Hi, my name is Helal from Bangladesh. I’ve been working with SDA agar in a food industry for long time,,,,, but still can’t Indentified Yeast growing on this media!!!! Please give some instructions, how to easily Indentified this organism????

    1. You can do a Gram’s stain and observe the hyphae with budding cells. They are Gram positive. You can also do the germ tube test by making a light suspension of 2 large colonies from your SAB agar in 0.5 mls of human or bovine serum. Incubate for 2-3hrs and do a wet mount. You’ll see the hyhae with budding cells. Hope this helps.

  11. DR P SHIVAKUMAR SINGH

    Excellent….

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