Asthma and lower airway disease
Indoor microbial communities: Influence on asthma severity in atopic and nonatopic children

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Background

Allergic and nonallergic asthma severity in children can be affected by microbial exposures.

Objective

We sought to 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. 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 levels). Microbial community structure and concentrations in house dust were determined by using next-generation DNA sequencing and quantitative PCR. 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 an increased concentration of summed allergenic fungal species, high total fungal concentrations, and high bacterial richness by using logistic regression in addition to microbial community composition by using the distance comparison t test. Asthma severity in atopic children was associated with fungal community composition (P = .001). By using logistic regression, asthma severity in nonatopic children was associated with total fungal concentration (odds ratio, 2.40; 95% CI, 1.06-5.44). The fungal genus Volutella was associated with increased asthma severity in atopic children (P = .0001, q = 0.04). The yeast genera Kondoa might be protective; Cryptococcus species might also affect asthma severity.

Conclusion

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

Section snippets

Study population

The current analysis was designed to select participants of the parent study at the extremes of asthma severity stratified by atopic status while controlling for socioeconomic status, asthma medication use, and sampling season. Subjects for the present analysis (n = 200) were selected from participants in a study of air quality and respiratory health.14, 15 Between 2006 and 2009, children with asthma and their families were recruited from Connecticut and southwestern Massachusetts.14, 15

Results

Demographic information for the participants is shown in Table II. By using χ2 analysis, distributions were representative for the variables age, race, sex, mother's education level, or smoking in the home between subjects in the 4 atopy/asthma severity categories (P > .05). Compared with the parent study cohort, sex distribution was representative (P = .47), although the current study group is less white (P < .0001) and the mother's education level is lower (P = .004).

Sequencing results have

Discussion

Our results suggest that asthma severity in children is associated with microbial exposures. The observed response might be different in atopic compared with nonatopic children, which deserves further study. Among all children, associations were found with both fungal and bacterial variables (Fig 1, A, and Table III). Asthma severity in atopic children was associated with fungal community composition (Fig 2). There was also a trend toward increased asthma severity with exposure to summed

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    Supported by the Alfred P. Sloan Foundation (Microbiology of the Build Environment) and a grant from the National Institutes of Health (ES05410).

    Disclosure of potential conflict of interest: B. P. Leaderer receives research support from National Institute of Environmental Health Sciences ES05410. J. Peccia receives research support from the Alfred P. Sloan Foundation. The rest of the authors declare that they have no relevant conflicts of interest.

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