Spatiotemporal variation of the indoor mycobiome in daycare centers

Abstract

Background Children spend considerable time in daycare centers in parts of the world and are exposed to the indoor micro- and mycobiomes of these facilities. The level of exposure to microorganisms varies within and between buildings, depending on occupancy, climate, and season. In order to evaluate indoor air quality, and the effect of usage and seasonality, we investigated the spatiotemporal variation in the indoor mycobiomes of two daycare centers. We collected dust samples from different rooms throughout a year and analyzed their mycobiomes using DNA metabarcoding. Results The fungal community composition in rooms with limited occupancy (auxiliary rooms) was similar to the outdoor samples, and clearly different from the rooms with higher occupancy (main rooms). The main rooms had higher abundance of Ascomycota, while the auxiliary rooms contained comparably more Basidiomycota. We observed a strong seasonal pattern in the mycobiome composition, mainly structured by the outdoor climate. Most markedly, basidiomycetes of the orders Agaricales and Polyporales, mainly reflecting typical outdoor fungi, were more abundant during summer and fall. In contrast, ascomycetes of the orders Saccharomycetales and Capnodiales were dominant during winter and spring. Conclusions Our findings provide clear evidences that the indoor mycobiomes in daycare centers are structured by occupancy as well as outdoor seasonality. We conclude that the temporal variability should be accounted for in indoor mycobiome studies and in the evaluation of indoor air quality of buildings.

The bacterial community of childcare centers: potential implications for microbial dispersal and child exposure

“…Thus, understanding the indoor fungal diversity could further our understanding of age-specific exposure pathways and transmission. For example, a recent study showed that less-occupied rooms in childcare centers were significantly different from the main rooms in fungal diversity, [ 21 ]. These findings, in addition to our own, have implications for understanding age-specific exposure to microbes and fungi and their different health outcomes [ 64 ], and highlights why studies on the microbiome of the built environment occupied by different age groups are important.…”

“…Sources of fungi in the indoor environment include building materials, ventilation systems, human transmission (i.e. through fungi tracked into the building from environmental sources), and the greater outdoor environment [ 21 , 23 ], with indoor fungal communities in childcare centers dominated by the genera Aspergillus, Cladosporium, Penicillium, Alternaria, Rhizopus and Curvularia. High abundances of these fungi in built environments have been associated with various respiratory disorders such as asthma and allergic rhinitis [ 24 , 25 ].…”

The Indoor Mycobiomes of Daycare Centers Are Affected by Occupancy and Climate

“…Similarly, in a study investigating indoor fungi in a housing facility in California, Adams et al showed that the outdoor air and not the residents structured the indoor mycobiome ( 12 ). Interestingly, in our recent study on the seasonality of the indoor mycobiome, the indoor environment was more influenced by the outdoor fungal diversity during summer and fall ( 10 ). Thus, as the community scientists in the present study performed sampling during early spring, we may have detected a stronger influence of indoor variables than, e.g., Shin et al ( 30 ), where samples were collected from August to October in a comparable climate in South Korea.…”

“…In line with this, it was previously shown that the concentration of fungi in daycare centers is higher than that in homes ( 9 ). In several studies, the outdoor environment has been reported to be the main source of indoor fungi ( 10 – 13 ) due to the influx of spores through windows, entrances, and the ventilation system. Hence, the vegetation and climate that structure the outdoor fungi will indirectly also structure the indoor mycobiome ( 11 ).…”

“…DNA metabarcoding, based on high-throughput sequencing of PCR-amplified markers, is established as an effective approach to survey fungal communities ( 21 ). In buildings, DNA metabarcoding of dust samples, integrating spores and hyphal remains that have accumulated over time, has proven to be an effective means for exploring the indoor mycobiome ( 10 , 12 , 13 , 22 , 23 ). However, it might be difficult to get access and obtain samples from a representative number of buildings.…”