Isolation of filamentous basidiomycetes from respiratory samples in a tertiary care Spanish hospital.

Background: The clinical significance of the filamentous basidiomycetes isolated from clinical samples is not always clear. Thus, these fungi have been considered environmental contaminants traditionally.

Aims: To review those clinical cases in which filamentous basidiomycetes from respiratory samples had been isolated.

Methods: The retrospective study was carried out in a single tertiary care hospital. We recovered all culture-confirmed isolations of filamentous basidiomycetes from respiratory samples (bronchial aspirate [BAS], bronchoalveolar lavage [BAL] and sputum) analyzed between the years 2020 and 2023. Isolates were identified by ITS region sequencing.

Results: In six patients a filamentous basidiomycete had been isolated from a respiratory sample. The species identified were all different: Fomitopsis sp. (BAS), Trametes ljubarskyi (BAL), Stereum gausapatum (BAS), Porostereum spadiaceum (BAS), Phlebia subserialis (sputum) and Inonotus levis (BAL). All the patients were immunosuppressed or had an underlying disease with pulmonary involvement. None of them received any specific antifungal treatment (in relation with the fungus isolated) and all six improved clinically and were discharged.

Conclusions: The isolation of filamentous basidiomycetes in these patients had uncertain clinical significance. However, the isolation of any filamentous basidiomycete in respiratory samples from immunosuppressed patients or patients with chronic pulmonary disease is an emerging situation that should be carefully assessed in the context of chronic allergic episodes or suspicion of invasive fungal infections.