Biodiversity and Environmental Microbiota of Early Childhood Education Centres: Exposure Determinents and Associations with Respiratory Health

Background: Modern lifestyles and urban development have reduced exposure to microbially rich environments, which may adversely affect immune development and health. The Biodiversity Hypothesis and the Farm Effect propose that exposure to greenspace, livestock, and farms, supports immune maturation through contact with diverse environmental microbiota. Early Childhood Education Centres (ECE) potentially represent a key environment of microbial exposure during a critical developmental stage. However, little is known about the microbiomes of these environments, the factors that shape it, or the association with health. Aims: This thesis characterised the microbiome of floor-dust and sandpits of ECEs in the Greater Wellington Region, and investigated the factors contributing to bacterial community differences within and between ECE sites. It also explored associations among plant-diversity exposure at ECE centres, microbial exposures, and childhood health outcomes. Methods: An observational study nested within The Urban/Rural Microbiome of Infants (TUMI) study investigated associations between plant-diversity exposure at ECE centres and the health outcomes of wheeze, colds, chest infection, flu, and ear infections in 493 children. Metagenomic sequencing of sandpit and floor-dust samples from 39 ECE centres was conducted to characterise the bacterial microbiome of ECEs and investigate determinants of bacterial variation. Associations between health outcomes and ECE microbial characteristics in 116 children were explored. Results: Sandpit and floor-dust samples were characterised by distinct bacterial communities; significantly lower alpha diversity observed for sandpits. Bacterial composition varied significantly between ECE centres. Local plant-diversity and landscape designs appeared to affect bacterial communities more strongly than plant-diversity further afield. Farm-like bacterial compositions were detected across ECE environments, with sandpits showing higher proportional levels and floor-dust showing higher overall loads. Higher plant-diversity at ECE centres was associated with reduced prevalence of colds and ear infections. Conclusion: This study demonstrates microbial exposures differ both within and between different ECE centres, with potential implications on child respiratory health.