The changing spectrum of Saccharomycotina yeasts causing candidemia: phylogeny mirrors antifungal susceptibility patterns for azole drugs and amphothericin B

ABSTRACT Ascomycetous yeast species belonging to the subphylum Saccharomycotina (Ascomycota, Fungi) may cause a variety of pathologies in humans. Candida albicans accounts for almost half of candidemia cases but the emergence of uncommon yeasts in the clinical setting is increasing. Here, we highlight the epidemiology of Saccharomycotina budding yeasts causing bloodstream infections, address antifungal susceptibility patterns and unravel how the latter corresponds to their phylogenetic relationship. Only studies applying Matrix Assisted Laser Desorption Ionization-Time of Flight Mass Spectrometry (MALDI-TOF MS) and/or sequence-based identification methods were considered. A ribosomal DNA-based phylogeny was used to present phylogenetic relationships of yeasts pathogens and their close relatives and to show how the antifungal susceptibility patterns for amphotericin B and azole drugs correlate with the clades found. Candida albicans was still the leading cause of yeast-related sepsis, but 22 other Saccharomycotina yeast species were also identified as a common cause of sepsis based on the literature. Similar minimum inhibitory concentration (MIC) values are found between phylogenetically closely related species and appear to be clade-specific to a large extent. This demonstrates that phylogeny may serve as a first guidance for treatment of emerging yeasts with uncommon susceptibility patterns due to intrinsic resistance. Epidemiology of yeasts causing bloodstream infections is reviewed, the most prevalent and frequent species are identified, and phylogeny and its relevance to antifungal susceptibility patterns of rare yeasts is presented.