Trichosporon asteroides Isolated from Cutaneous Lesions of a Suspected Case of “paracoccidioidomycosis ceti” in a Bottlenose Dolphin (Tursiops truncatus)

“Paracoccidioidomycosis ceti” is a rare zoonotic fungal infection affecting dolphins and is endemic worldwide. The causative agents are Paracoccidioides species; however, it is impossible to isolate the fungal species. We isolated Trichosporon asteroides from multifocal, irregularly raised skin lesions on a female bottlenose dolphin (Tursiops truncatus) captured off coast of Japan, which was suspected to have “paracoccidioidomycosis ceti.” An abundance of round, yeast-like cells was detected in a potassium hydroxide direct-mount specimen of the skin samples; however, nested PCR targeting the partial sequence of 43-kDa glycoprotein-coding gene correspondent to Paracoccidioides sp. was negative. Biopsied tissue samples were cultured on brain heart infusion agar plates supplemented with chloramphenicol, 1% yeast extract, and 4% sodium chloride (4% NaCl-BHI), on Mycosel agar with 4% sodium chloride (4% NaCl-Mycosel), and on potato dextrose agar supplemented with chloramphenicol (CPDA) at 35 °C for 4 weeks. Cream-colored and wrinkled colonies consisting of hyphae and arthroconidia grew on 4% NaCl-BHI and CPDA, while film-like colonies composed of arthroconidia and round yeast-like cells developed on 4% NaCl-Mycosel. Although these primary cultures resembled fresh isolates of P. brasiliensis, they were identified as Trichosporon asteroides based on routine mycological studies and the internal transcribed spacer regions of ribosomal RNA sequences. The results suggested that trichosporonosis caused by T. asteroides might remain latent among cases of “paracoccidioidomycosis ceti” diagnosed without cultures and molecular biological analysis.