2020 Volume 69 Issue 3 Pages 451-456
We report a case of pulmonary chromoblastomycosis caused by the viscous species Exophiala dermatitidis in a patient with nontuberculous mycobacterial (NTM) disease. Two years after the end of treatment for NTM disease, the patient coughed purulent sputum and developed chest pain. A sputum Gram staining test showed the patient to be positive for filamentous fungi. Colonies were isolated after culturing in a chromogenic Candida medium for 72 h and unstained viscous colonies were detected. Microscopic examination of these viscous colonies revealed a yeast-like fungus that was speculated to be a dimorphic fungal species of the Exophiala genus. It was identified to be Exophiala dermatitidis after analysis using a MALDI Biotyper and ITS region sequencing analysis. Because the same fungus was repeatedly detected in the sputum and exacerbation of the right middle lobe infiltration shadow was consistent with the deterioration of subjective symptoms, the patient was diagnosed as having pulmonary chromoblastomycosis. When colony viscosity was compared after culturing in chromogenic Candida agar, Sabouraud agar and CP-added potato dextrose agar, viscosity was first detected in the CP-added potato dextrose agar after 48 h of culture and after 72 h in the other two media. Because it takes time for the colonies of E. dermatitidis to turn black in color, early detection of the viscous colonies of E. dermatitidis becomes possible by using CP-added potato dextrose agar. Furthermore, it is important to test for colony viscosity during colony isolation.
