Sabourauddextroseagar

Sabouraud dextrose agar is a widely used culture medium designed for the isolation and growth of fungi, including yeasts and molds. It was developed by the French microbiologist Raymond Sabouraud in the late 19th century and is named after him. The medium exploits a relatively acidic pH to suppress bacterial growth, promoting fungal recovery from clinical or environmental samples.

Composition and variants: A typical Sabouraud dextrose agar formulation contains dextrose (glucose) as the primary carbon source and peptone as the nitrogen source, with agar for solidification. Common final concentrations are around 4% dextrose, 1% peptone, and 2% agar, with a final pH near 5.6. Commercial preparations may differ in exact proportions. To inhibit bacterial contaminants or to select certain fungi, antibiotics such as chloramphenicol or cycloheximide may be added. Variants include Sabouraud dextrose agar with chloramphenicol, and Mycosel agar, which adds cycloheximide and chloramphenicol for selective isolation of dermatophytes.

Preparation and use: The medium is prepared by dissolving components in water, adjusting the pH to about 5.6, and sterilizing by autoclaving. After cooling to approximately 45–50°C, antibiotics may be added if required and the medium poured into sterile Petri dishes. Plates are inoculated with specimens and incubated at roughly 25–30°C. Fungal colonies typically appear within several days, with morphology and pigmentation that aid identification.

Applications and limitations: SDA is a general-purpose medium in clinical, veterinary, and research mycology for culturing fungi. It supports a broad range of species but may be overgrown by faster-growing contaminants; antibiotic supplements help mitigate this. The acidic pH, while beneficial for fungi, makes the medium unsuitable for routine bacterial culture.