A clinical microbiology laboratory identifies a yeast isolate from a blood culture that is urease-positive. The organism produces mucoid colonies on Sabouraud dextrose agar and phenol oxidase-positive colonies on Niger seed agar. Which organism is this?

• A Candida glabrata
• B Candida krusei
• C Trichosporon asahii
• D Cryptococcus neoformans ✓

Explanation

Cryptococcus neoformans is urease-positive, distinguishing it from most Candida species. It produces phenol oxidase (polyphenol oxidase), which converts substrates in Niger seed agar to melanin, yielding brown colonies. D. glabrata and D. krusei are urease-negative. Trichosporon asahii is urease-positive but is a filamentous yeast that does not produce melanin on Niger seed agar and shows urease-positive arthroconidia.

Reference: Koneman's Color Atlas and Textbook of Diagnostic Microbiology, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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