Effects of Bioaerosol Aerodynamic Size on Biodiversity in Three Kindergartens in Taiwan

Abstract

Background: Human-associated bacteria (HAB) in the microbiome can become airborne bacterial aerosols (bioaerosols). The aerodynamic sizes of bioaerosols demonstrated may significantly affect their behaviors, respiratory deposition and biodiversity.Methods: The bacterial size, biodiversity and the HAB were evaluated at three kindergartens in central Taiwan in winter and spring. Kindergartens A, B, and C were in urban, semi-urban, and rural areas, respectively. A six-stage viable Andersen cascade impactor was used to collect bioaerosols and to determine their size distributions. A BD Phoenix-100 automated interpretation system was used to identify the species in those bioaerosols. The uniformity transformation was applied to verify the distributions of bacterial concentrations in different sampling rounds.Results: The results revealed 1,425 colonies (97.6%) that corresponded to 63 species in 29 genera and 35 colonies (2.4%) that were unidentified. The most abundant phylum was Actinobacteria (56.6+22.2%), Staphylococcus spp. was found in all sampling rounds, with a range of abundance between 2.0 and 70.0%. In all rounds, the geometric mean diameter of the bioaerosol and the geometric standard deviation of the bioaerosol size ranged from 2.19 to 5.42 µm and from 1.66 to 2.70, respectively. The Shannon diversity (H) and inverse Simpson diversity index (D) of the bioaerosols at each kindergarten were positively correlated with bioaerosol size, as larger bioaerosols had higher values of the biodiversity metrics. The Pearson correlations of H with the urbanization of the area of the kindergarten, temperature, RH and CO2 concentration were statistically significant (P < 0.05), indicating that the environmental variables and biodiversity covaried. The biodiversity in the rural area exceeded that in the urban area. Multiple and stepwise regression revealed that bioaerosol size was statistically significant with H (P = 0.001) and D (P = 0.002). The study may improve our understanding of the mechanisms and epidemiological spread of airborne infections.