Question:medium
Which of the following fungi is difficult to isolate in culture?
Which of the following fungi is difficult to isolate in culture?
Show Hint
Look for the lipid-dependent yeast that will not grow on plain Sabouraud agar.
Updated On: Jun 24, 2026
- Candida
- Dermatophytes
- Cryptococcus
- Malassezia furfur
Show Solution
The Correct Option is D
Solution and Explanation
Step 1: The ease of growing a fungus depends on whether it has any unusual nutritional demand. Standard Sabouraud agar supports the common pathogens, but a lipid-craving organism needs extra fat added to the plate.
Step 2: Malassezia furfur is exactly such an organism. Being lipophilic, it stays inert on plain Sabouraud medium and only thrives when oil, for instance 1 percent emulsified olive oil, or a tailored Dixon (or modified Dixon) medium is provided. That dependence makes it the troublesome isolate, so (d) wins.
Step 3: By contrast, Candida species, the dermatophytes, and Cryptococcus neoformans all colonise routine Sabouraud agar without fuss and are considered easy laboratory growers.
Step 4: This fastidious nature fits its life on oily, sebaceous skin, where it produces the hypopigmented or hyperpigmented patches of pityriasis versicolor.
\[\boxed{\text{Malassezia furfur}}\]
Step 2: Malassezia furfur is exactly such an organism. Being lipophilic, it stays inert on plain Sabouraud medium and only thrives when oil, for instance 1 percent emulsified olive oil, or a tailored Dixon (or modified Dixon) medium is provided. That dependence makes it the troublesome isolate, so (d) wins.
Step 3: By contrast, Candida species, the dermatophytes, and Cryptococcus neoformans all colonise routine Sabouraud agar without fuss and are considered easy laboratory growers.
Step 4: This fastidious nature fits its life on oily, sebaceous skin, where it produces the hypopigmented or hyperpigmented patches of pityriasis versicolor.
\[\boxed{\text{Malassezia furfur}}\]
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