The relationship between fungal diversity in house dust and childhood asthma development

Abstract

Background: Childhood asthma prevalence has increased in recent decades. A relationship between early fungal diversity exposure and later asthma development, per the hygiene hypothesis, has not been established due to the absence of quantitative, unbiased techniques to measure fungal diversity. Aims: We used next-generation DNA sequencing to quantitatively evaluate fungal taxa and diversity in house dust samples without the biases of culturing. This research aims to characterize relationships among fungal taxa and diversity in house dust, measured wall moisture, and later asthma development in children. Methods: House dust and environmental measurements, including wall moisture, were collected in the CHAMACOS birth cohort study in Salinas, CA at child age 12 months. Current asthma status was evaluated at age 7 years in the available 292 children. A nested case-control analysis included 13 asthma cases and 28 controls. Dust was analyzed by 454 pyrosequencing to determine fungal identifications and diversity (number of different species per normalized sample). Results: Children from homes with low fungal diversity had an odds ratio of 4.8 (95% confidence limits 1.04-22.1) for developing asthma, not due to confounding. Homes with high measured moisture had increased fungal diversity. Negative confounding by moisture partially obscured the relationship between fungal diversity and asthma. No fungal taxa (species, genus, class) were significantly more common in asthma case homes but some taxa were significantly more common in control homes. Over 30 unique fungal taxa were significantly associated with moisture or mold indicators. Conclusions: This study avoided fungal culturing biases by using next-generation DNA sequencing to evaluate fungal diversity and taxa in house dust. Our findings suggest that low fungal diversity is associated with childhood asthma development.