Public health implications of airborne Candida : viability, drug resistance, and genetic links to clinical strains

Abstract

Candida is the largest genus of medically significant yeasts, causing diseases ranging from mucosal to life-threatening invasive infections. Airborne transmission of Candida has gained attention following its genotypic detection in ambient air and isolation in occupational air. However, more comprehensive phenotypic evidence, including viability, antifungal resistance, and phylogenetic relatedness to clinical strains, is needed in ambient air, with implications for community-level exposure, colonization, and infection. To address this gap, we sampled air at an urban and a coastal site using six-stage Andersen impactors. Viable isolates of C. parapsilosis, C. albicans, and C. tropicalis─all World Health Organization priority fungal pathogens─were recovered from ambient urban air, primarily associated with respirable particle sizes (2.1–7 μm) across seasons. Antifungal susceptibility testing identified C. parapsilosis as the predominant multidrug-resistant species. Whole-genome sequencing revealed airborne C. parapsilosis shared 99.53% genetic similarity with nearby clinical strains, differing by only 94 out of 20,206 single-nucleotide polymorphisms. This suggests the plausibility of community-acquired infection via airborne routes. These findings highlight the need to investigate airborne transmission from environmental reservoirs to human colonization and infection. This is particularly critical under urban megatrends and climate change, emphasizing an emerging microbial hazard beyond antibiotic-resistant bacteria within the One Health framework.