Background

Allergic and non-allergic asthma severity in children can be affected by microbial exposures.

Objective

Examine associations between exposures to household microbes and childhood asthma severity stratified by atopic status.

Methods

Participants (n=196) were selected from a cohort of asthmatic children in Connecticut and Massachusetts, USA. Children were grouped according to asthma severity (mild with no or minimal symptoms and medication, or moderate to severe persistent) and atopic status (determined by serum IgE). Microbial community structure and concentrations in house dust were determined using next-generation DNA sequencing and quantitative Polymerase Chain Reaction. Logistic regression was used to explore associations between asthma severity and exposure metrics, including richness, taxa identification and quantification, community composition, and concentration of total fungi and bacteria.

Results

Among all children, increased asthma severity was significantly associated with elevated concentration of summed allergenic fungal species, high total fungal concentration, and high bacterial richness by logistic regression, in addition to microbial community composition by distance comparison t-test. Asthma severity in atopic children was associated with fungal community composition (p=0.001). By logistic regression, asthma severity in non-atopic children was associated with total fungal concentration: odds ratio 2.40, 95% confidence interval 1.06–5.44. The fungal genus Volutella was associated with increased asthma severity in atopic children (p=0.0001, q=0.04). Yeast genera Kondoa may be protective; Cryptococcus may also impact asthma severity.

Conclusion

Asthma severity among this cohort of children was associated with microbial exposure, and associations differed based on atopic status.