Clinical and Hospital Environmental Fusarium in Taiwan: Molecular Identification, Antifungal Susceptibilities, and Phylogenetic Analyses

Background: Fusarium species are emerging pathogens known to cause both superficial and disseminated human infections. Aerosolized Fusarium species in healthcare settings have been associated with nosocomial fusariosis, particularly in patients with severe immunosuppression. Objectives: To analyse the phylogenetic relationships of clinical and hospital environmental Fusarium isolates and assess their susceptibility to available antifungal agents. Methods: Clinical Fusarium isolates were procured from four hospitals in Taiwan, with environmental air and water sampling collected at Kaohsiung Chang Gung Memorial Hospital (KCGMH). All clinical and hospital environmental Fusarium isolates were identified through gene sequencing of translation elongation factor 1-α and internal transcribed spacer regions of ribosomal DNA. Antifungal susceptibility testing followed the CLSI M38-A3 broth microdilution method. Results: A total of 41 clinical and 4 hospital environmental Fusarium isolates were identified, belonging to five species complexes (SC): F. solani SC (FSSC) (62.8%), F. fujikuroi SC (FFSC) (14.0%), F. incarnatum-equiseti SC (11.6%), F. dimerum SC (7.0%), and F. oxysporum SC (4.7%). Phylogenetic analysis revealed that clinical Fusarium isolates from KCGMH were closely related to environmental Fusarium isolates from air samples at the same hospital. Amphotericin B exhibited high activity against most Fusarium species. With the exception of FFSC, other Fusarium SC demonstrated significantly elevated MIC values to itraconazole, voriconazole, posaconazole, and isavuconazole. Conclusions: FSSC was the most prevalent SC in Taiwan, exhibiting higher MIC values for azoles than FFSC isolates. The clinical Fusarium isolates were observed to form clusters with the corresponding environmental isolates. The potential of airborne nosocomial infections in the healthcare environment cannot be overlooked.