Metagenomic insights into the bioaerosols in the indoor and outdoor environments of childcare facilities

Abstract

Airborne microorganisms have significant effects on human health, and children are more vulnerable to pathogens and allergens than adults. However, little is known about the microbial communities in the air of childcare facilities. Here, we analyzed the bacterial and fungal communities in 50 air samples collected from five daycare centers and five elementary schools located in Seoul, Korea using culture-independent high-throughput pyrosequencing. The microbial communities contained a wide variety of taxa not previously identified in child daycare centers and schools. Moreover, the dominant species differed from those reported in previous studies using culture-dependent methods. The well-known fungi detected in previous culture-based studies (Alternaria, Aspergillus, Penicillium, and Cladosporium) represented less than 12% of the total sequence reads. The composition of the fungal and bacterial communities in the indoor air differed greatly with regard to the source of the microorganisms. The bacterial community in the indoor air appeared to contain diverse bacteria associated with both humans and the outside environment. In contrast, the fungal community was largely derived from the surrounding outdoor environment and not from human activity. The profile of the microorganisms in bioaerosols identified in this study provides the fundamental knowledge needed to develop public health policies regarding the monitoring and management of indoor air quality.

Fig 1. Principal coordinate analysis (PCoA) of the (A) bacterial and (B) fungal communities in childcare facilities.

Fifty samples were collected from the indoor (blue symbols) and outdoor (red symbols) air of five daycare centers (sites A–E, circles) and five elementary schools (sites F–J, triangles). Differences in the composition of the microbial communities were quantified using the weighted UniFrac distance metric. The green dotted lines and circles indicate pairs of indoor and outdoor samples from the same sampling site. The distinctive bacterial community structures in the indoor and outdoor air were supported by the p-values determined by Wilcoxon t-test.

Fig 2. Relative abundance of bacteria identified at the genus level in indoor and outdoor air.

The sampling sites and replicates are indicated as letters and numbers, respectively, shown in columns. The taxonomic groups that had an average abundance >1.2% are shown.

Fig 3. Fungi in indoor and outdoor air identified at the phylum and class levels.

The inner circles indicate the composition of fungal reads at the phylum level, and the outer circles indicate the composition of the fungal community at the class level.

Fig 4. Relative abundance of four allergenic fungi in indoor and outdoor air samples.

The solid black lines represent the medians, and the circles are outliers. Bars denote the minimum and maximum values excluding the outliers.