Antifungal Susceptibilities of Rare Yeast Isolates

The recent increase in the number of rare yeasts isolated from clinical specimens is a cause for concern, requiring accurate identification of these yeasts and assessment of their antifungal susceptibility to guide treatment. In this regard, we identified 196 rare yeasts isolated from various clinical specimens, mostly urine and respiratory tract specimens of patients hospitalized in intensive care unit and wards, using MALDI-TOF MS, and assessed their susceptibility to amphotericin B, fluconazole, voriconazole, posaconazole, itraconazole, isavuconazole and anidulafungin using the EUCAST broth microdilution method. Among the rare yeast species we isolated, Candida lusitaniae (13.8%) was the most common, followed by Magnusiomyces capitatus (13.3%), Candida fabianii (12.2%), and Trichosporon asahii (11.7%). Antifungal susceptibility testing revealed high echinocandin MIC values against Magnusiomyces spp., Trichosporon spp., and Rhodotorula mucilaginosa isolates. Similarly, we found high MIC values for fluconazole against the isolates of Magnusiomyces spp., T. asahii, R. mucilaginosa, and several Candida spp., including Candida guilliermondii, Candida pararugosa, Candida rugosa, Candida pelliculosa, Candida norvegensis, and Candida fabianii. We found similar MIC values across phylogenetically closely related species. In conclusion, prompt identification of rare yeasts and assessment of their antifungal susceptibilities are essential for effective treatment of the infections they cause.