A 22-year-old man presents with hypopigmented macules with fine scaling over the chest and back. KOH mount of the scrapings shows round budding yeast cells mixed with short curved hyphae. Which property of this organism explains why routine fungal culture fails unless a special supplement is added?
- A It requires lipids such as olive oil or Tween for growth ✓
- B It is an obligate intracellular parasite
- C It requires an incubation temperature of 37 degrees Celsius
- D It grows only on media containing cycloheximide
Correct answer: A. It requires lipids such as olive oil or Tween for growth
Explanation
The KOH picture of round yeast cells with short curved hyphae is the classic 'spaghetti and meatballs' appearance of Malassezia furfur, the cause of pityriasis versicolor. Malassezia is a lipid-dependent organism and grows only when the medium is overlaid with olive oil or supplemented with Tweens, which is why ordinary Sabouraud dextrose agar fails. It grows readily at room temperature, is a surface colonising yeast rather than an intracellular pathogen, and cycloheximide is used to suppress contaminants, not to support this organism.
Reference: Jawetz, Melnick & Adelberg's Medical Microbiology, 27th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.