Pathogenic Budding Yeasts Isolated outside of Clinical Settings

Abstract

Budding yeasts are distributed across a wide range of habitats, including as human commensals. However, under some conditions, these commensals can cause superficial, invasive, and even lethal infections. Despite their importance to human health, little is known about the ecology of these opportunistic pathogens, aside from their associations with mammals and clinical environments. During a survey of approximately 1000 non-clinical samples across the United States of America, we isolated 54 strains of budding yeast species considered opportunistic pathogens, including Candida albicans and Candida (Nakaseomyces) glabrata. We found that, as a group, pathogenic yeasts were positively associated with fruits and soil environments, while the species Pichia kudriavzevii (syn. Candida krusei syn. Issatchenkia orientalis) had a significant association with plants. These results suggest that pathogenic yeast ecology is more complex and diverse than is currently appreciated and raises the possibility that these additional environments could be a point of contact for human infections.\n\nImportanceWe isolated several opportunistic pathogenic species of yeasts from the subphylum Saccharomycotina from multiple non-clinical environments across the United States of America. Among those strains isolated, over 50% represent the most common opportunistic pathogens. These species, C. albicans, Candida tropicalis, Candida parapsilosis, and C. glabrata, have been rarely isolated from non-clinical settings and have been usually interpreted as contamination. Our extensive isolations from natural settings challenge this assumption, suggesting that opportunistic pathogens can persist in alternative niches and that their ecology may be more complicated than is currently assumed. Non-clinical environments could be a short-term habitat as these yeasts are passed between their predominant hosts, endothermic animals.