Selective media in medical mycology: what does Sabouraud medium isolate? Selective media promote growth of target organisms while suppressing others. Sabouraud dextrose agar is primarily used to selectively isolate which group from clinical or food samples?

Introduction / Context:Sabouraud dextrose agar (SDA) is a cornerstone medium in medical mycology. Its low pH and specific nutrient composition discourage many bacteria and favor fungal growth. Knowing its purpose streamlines specimen processing in clinical labs.

Given Data / Assumptions:

• SDA typically has a pH around 5.6 and high dextrose content.
• Antibiotics may be added to further suppress bacteria.
• Objective: recover yeasts (for example, Candida spp.) and molds (for example, dermatophytes).

Concept / Approach:

Lower pH and nutrient profile permit robust fungal growth while inhibiting many bacterial contaminants. Thus, Sabouraud medium is selective for fungi, especially yeasts and molds, in mixed clinical and environmental samples.

Step-by-Step Solution:

Verification / Alternative check:

Clinical guidelines recommend SDA (with or without antibiotics/cycloheximide variants) for primary isolation of fungi from skin, nail, mucosal, and other specimens.

Why Other Options Are Wrong:

• Coliforms and Gram-positive bacteria: Growth inhibited by pH/antibiotics; media like MacConkey or mannitol salt agar are more appropriate.
• Acid-fast organisms: Require specialized media (for example, Lowenstein–Jensen), not SDA.
• Protozoa: Not cultured on SDA in routine bacteriology/mycology.

Common Pitfalls:

• Assuming SDA differentiates Candida species; it is not differential without additional tests.

Final Answer:

Yeasts (and filamentous fungi)