Fungal burden assessment in hospital zones with different protection degrees

• Cultivation and particle counting revealed a fungal burden gradient in hospitals. • 74 fungal genera were identified from the hospital environment (air and surfaces). • Cladosporium, Penicillium, Aspergillus, Alternaria and Aureobasidium were prevalent. • 36 identified fungal species were previously reported as human pathogens. • A fungal collection of 508 hospital-environment isolates has been generated. Hospital-dwelling fungi can cause life-threatening invasive infections in patients with impaired immune system. To prevent them, fungal diversity knowledge and environmental monitoring protocols in healthcare settings should be improved. This study contributes to these challenges through a multifaceted approach, combining air and surface sampling, particle counting, cultivation and DNA-based identification of isolates, to characterize fungal load and diversity in three tertiary care hospitals. Three indoor zones with different protection degree (unprotected admission halls and waiting rooms, clean regular patient rooms, and HEPA-protected intensive care units) are compared with the outdoor conditions, and the clinical relevance of the identified hospital fungi is discussed. Results of particle and colony counts were highly correlated and showed a common indoor decreasing gradient, from the most exposed and occupied zone near the entrances to the HEPA-protected zone, in the three hospitals and two 6-month-apart surveys. They presented a high fungal diversity (74 genera) dominated by Cladosporium, Penicillium, Aspergillus, Alternaria and Aureobasidium , which were prevalent in different zones and substrata (air and surfaces). In addition, skin-associated yeasts such as Naganishia, Moliniella, Rhodotorula and Filobasidium were especially abundant in regular patient rooms. Based on previous clinical literature, 36 species were identified as opportunistic human pathogens including filamentous fungi (e.g. Aspergillus spp. Talaromyces spp. and Mucorales) and yeasts (e.g. Candida parapsilosis, Rhodotorula mucilaginosa, Filobasidium magnum and Clavispora lusitaniae ). The generated culture collection, composed of 508 isolates from air (69 %) and surfaces (31 %), is a valuable resource for further research combining environmental and clinical mycology in buildings.