Is the Exophiala complex a silent threat in Brazil? A systematic review

The genus Exophiala comprises melanized (dematiaceous) fungi found worldwide, with a higher prevalence in tropical regions. In this study, we examined the occurrence of Exophiala species in clinical and environmental samples across Brazil and documented their presence in human, animal, and environmental sources. Ten isolates, suspected of belonging to Exophiala spp. were analyzed using a polyphasic taxonomic approach based on phenotypic characterization and partial sequencing of the internal transcribed spacer (ITS1-5.8 S-ITS2) region of ribosomal DNA. Additionally, a molecular approach employing Colony PCR with a rapid, microwave-optimized DNA extraction method for dematiaceous fungi was also applied. As part of the study, a systematic review of 26 published reports was also conducted. Exophiala dermatitidis was the most frequently reported species in Brazil. Molecular analyses confirmed that all fungal samples included in this study belonged to this species. The rapid microwave-based DNA extraction method, combined with Colony PCR and adapted here for dematiaceous fungi, proved to be an efficient approach for obtaining and amplifying DNA in Exophiala spp. To the best of our knowledge, this is the first report of E. dermatitidis isolated from marmosets, mussels, sardines, sewage, and bats in Rio de Janeiro, Brazil. These findings advance our understanding of the circulation of E. dermatitidis across different hosts and environments, emphasizing the importance of continuous surveillance and further studies to clarify its role as a potentially emerging pathogen.