Abstract
Abstract Background Exophiala dermatitidis is a black fungus isolated from wet environments such as soil and baths. Human infections have been reported chiefly as skin and soft tissue infections, and respiratory infections have been extremely rare. The fungus is dimorphic and known to be yeast-like in culture, changing to filamentous fungi over time. The fungus is often misidentified as yeast during the first few days of culture, and preliminary experiments have shown that it can be misidentified as Rhodotorula spp. by commercially available yeast identification kits. Methods Genetic identification was performed using 44 strains isolated from airway specimens over the past 11 years from July 2012 to September 2023, except for one difficult to culture, by determining the sequence of the ITS and D1/D2 regions. Cases genetically identified with E. dermatitidis were examined retrospectively for clinical information except for seven cases identified of the same cases. Results Of the 43 strains identified genetically, 22 were identified as E. dermatitidis, indicating that they were misidentified in approximately 50% of the cases; analysis of the clinical information of the 15 cases identified as E. dermatitidis and for which a retrospective search was possible showed that chronic lower respiratory tract infection or pneumonia due to E. dermatitidis was definite in six cases, active infection was possible in five cases and airway colonization only in four cases. Comorbidities included pulmonary non-tuberculosis mycobacterium (NTM) in five cases, chronic progressive pulmonary aspergillosis (CPPA) in three cases, and pulmonary nocardiosis in one case, suggesting concurrent chronic pulmonary infections due to other microbes. Steroid and immunosuppressive agent use was observed in ten cases. Five of the six definite cases responded to azoles, and one case resolved spontaneously with only a reduction of the immunosuppressive drugs. Drug sensitivity testing showed that all cases were resistant to Candin and sensitive to azoles and polyenes. Conclusion E. dermatitidis is a dimorphic fungus that is time-consuming to culture and may have been underestimated previously, misidentified as Rhodotorula spp. In addition to NTM and CPPA, E. dermatitidis might be differentiated in chronic lung infections. Disclosures Hiroshi Mukae, M.D., Ph.D., AstraZeneca: Lecture fees|Gilead Sciences: Lecture fees|GSK: Lecture fees|MSD: Advisor/Consultant|MSD: Lecture fees|Pfizer: Lecture fees|Shionogi & Co., Ltd.: Advisor/Consultant|Shionogi & Co., Ltd.: Grant/Research Support|Shionogi & Co., Ltd.: Lecture fees
Published Version
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