Seasonal structural characteristics of indoor airborne fungi in library rooms by culturing and high-throughput sequencing

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In public buildings such as libraries, people are more prone to airborne microbial cross-infection. Therefore, the present study uses cultivation and high-throughput sequencing techniques to explore the seasonal structural characteristics of indoor airborne fungi within four library rooms, and determines the fungal composition on the surface of commonly used books. The results showed that the highest mean fungal propagule concentrations were 634 ± 210 CFU m−3, 534 ± 177 CFU m−3, 780 ± 294 CFU m−3, and 681 ± 227 CFU m−3, and these values were found in the autumn in each room. In all four rooms, the fungal propagule with the highest concentrations had sizes ranging from 1.1 to 3.3 μm in each season which can penetrate to the lower respiratory tract. The dg values (2.62–3.17 μm) of the airborne fungi for all four seasons in each room can reach the secondary bronchi. There was little overlap among the dominant fungal genera across the four seasons in each room, and most of the dominant genera were opportunistic pathogenic or allergenic fungi (Torula, Cladosporium, Candida, Malassezia, Aureobasidium, Gibberella, and Aspergillus). Students and staff members were exposed to the higher levels of airborne fungal propagules in autumn. Five abiotic parameters have seasonal effects on the airborne fungal propagule concentrations. Moreover, four fungal genera from the sampled books were determined to be potential biodegradation. Overall, the information provided by this study will help to strengthen our understanding of indoor airborne fungal pollution and spread in public buildings.