Sabouraud Dextrose Broth (SDB): Principle, Composition, Preparation, and Applications in Microbiology

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Sabouraud Dextrose Broth (SDB): Principle, Composition, Preparation, and Applications in Mycology

Sabouraud Dextrose Broth (SDB) is a nutrient-rich liquid medium used extensively in microbiology for the cultivation of yeasts, molds, and pathogenic fungi. It is particularly useful in clinical, pharmaceutical, and environmental microbiology for detecting fungal contamination or for maintaining fungal stock cultures. The formulation was originally developed by Raymond Sabouraud in the late 19th century to support the growth of dermatophytes.

Principle of Sabouraud Dextrose Broth (SDB)

The principle of Sabouraud Dextrose Broth lies in its ability to provide a carbon source (dextrose) and nitrogenous compounds (peptones) that promote fungal growth. The acidic pH (typically around 5.6 ± 0.2) favors the proliferation of fungi and yeasts while inhibiting most bacterial contaminants. This selective nature makes SDB a preferred choice for isolating and cultivating fungal species in laboratory testing.

Composition of Sabouraud Dextrose Broth (SDB)

Ingredients Gram/Liter Purpose
Peptone (Casein or Meat) 10.0 g Provides nitrogen, vitamins, and amino acids for fungal growth.
Dextrose (Glucose) 40.0 g Primary carbon and energy source for yeasts and molds.
Final pH (at 25°C) 5.6 ± 0.2 Acidic pH supports fungi and suppresses most bacteria.

Preparation of Sabouraud Dextrose Broth (SDB)

  1. Weigh 50 grams of Sabouraud Dextrose Broth powder and dissolve it in 1 liter of distilled water.
  2. Mix thoroughly to ensure the medium is completely dissolved.
  3. Distribute the medium into flasks or culture tubes as required (usually 10–20 mL per tube).
  4. Adjust the pH to 5.6 ± 0.2 if necessary using 1N HCl or 1N NaOH.
  5. Sterilize the medium by autoclaving at 121°C for 15 minutes.
  6. After sterilization, allow the broth to cool before inoculating the sample or culture.

Storage

Store the prepared or dehydrated medium in a cool, dry place (below 25°C), protected from light and moisture. Avoid repeated heating or freezing.

Applications of Sabouraud Dextrose Broth (SDB)

  • Isolation and cultivation of fungi, molds, and yeasts from clinical and environmental samples.
  • Used for fungal contamination testing in pharmaceutical and cosmetic products.
  • Maintenance of fungal stock cultures for laboratory and research purposes.
  • Employed in antifungal susceptibility testing and growth studies.
  • Used as an enrichment medium for pathogenic fungi such as Candida, Aspergillus, and Trichophyton species.

Quality Control (QC) Organisms

For quality assurance, the following standard organisms are recommended for growth performance testing:

Organism Expected Growth
Candida albicans (ATCC 10231) Good growth
Aspergillus niger (ATCC 16404) Good growth (filamentous form)
Escherichia coli (ATCC 25922) Inhibited or poor growth

Precautions

  • Do not overheat the medium; excessive heating can caramelize dextrose and affect fungal growth.
  • Maintain aseptic conditions while handling fungal cultures to prevent contamination.
  • Always use appropriate biosafety precautions when working with pathogenic fungi.

Result Interpretation

After incubation at 25°C to 30°C for 48–72 hours (yeasts) or up to 7 days for molds, fungal growth can be observed as turbidity, pellicle formation, or mycelial mat depending on the organism. The presence of visible growth confirms the presence of viable fungal cells in the sample.

Conclusion

Sabouraud Dextrose Broth (SDB) is an indispensable culture medium in mycology and microbiological analysis. Its selective acidic environment, nutrient composition, and simplicity make it ideal for the detection, growth, and maintenance of fungi and yeasts in pharmaceutical, food, and clinical laboratories.

— Written by a Microbiology Expert | For Educational & Laboratory Reference

💬 About the Author

Siva Sankar is a Pharmaceutical Microbiology Consultant and Auditor with extensive experience in sterility testing, validation, and GMP compliance. He provides consultancy, training, and documentation services for pharmaceutical microbiology and cleanroom practices.

📧 Contact: siva17092@gmail.com
Mobile: 09505626106

📱 Disclaimer: This article is for educational purposes and does not replace your laboratory’s SOPs or regulatory guidance. Always follow validated methods and manufacturer instructions.

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