Asthma and lower airway disease
Asthma-associated differences in microbial composition of induced sputum

https://doi.org/10.1016/j.jaci.2012.11.013Get rights and content

Background

It is increasingly evident that microbial colonization of the respiratory tract might have a role in the pathogenesis of asthma.

Objective

We sought to characterize and compare the microbiome of induced sputum in asthmatic and nonasthmatic adults.

Methods

Induced sputum samples were obtained from 10 nonasthmatic subjects and 10 patients with mild active asthma (8/10 were not using inhaled corticosteroids). Total DNA was extracted from sputum supernatants and amplified by using primers specific for the V6 hypervariable region of bacterial 16s rRNA. Samples were barcoded, and equimolar concentrations of 20 samples were pooled and sequenced with the 454 GS FLX sequencer. Sequences were assigned to bacterial taxa by comparing them with 16s rRNA sequences in the Ribosomal Database Project.

Results

All sputum samples contained 5 major bacterial phyla: Firmicutes, Proteobacteria, Actinobacteria, Fusobacterium, and Bacteroidetes, with the first 3 phyla accounting for more than 90% of the total sequences. Proteobacteria were present in higher proportions in asthmatic patients (37% vs 15%, P < .001). In contrast, Firmicutes (47% vs 63%, P = .17) and Actinobacteria (10% vs 14%, P = .36) were found more frequently in samples from nonasthmatic subjects, although this was not statistically significant. Hierarchical clustering produced 2 significant clusters: one contained primarily asthmatic samples and the second contained primarily nonasthmatic samples. In addition, samples from asthmatic patients had greater bacterial diversity compared with samples from nonasthmatic subjects.

Conclusion

Patients with mild asthma have an altered microbial composition in the respiratory tract that is similar to that observed in patients with more severe asthma.

Section snippets

Subjects and sputum samples

Induced sputum samples from 10 patients with physician-diagnosed active asthma and 10 nonasthmatic adults were obtained for this study. The samples were collected as part of the ongoing Tucson Children's Respiratory Study, a nonselected birth cohort whose participants are now adults in their early 30s.13 Asthma, wheeze, bronchitis, and smoking information was collected from participant-completed questionnaires at age 26 years. Spirometry was completed according to American Thoracic Society

Results

Characteristics of the study subjects are presented in Table I.15 All subjects were part of a longitudinal study of the natural history of asthma in a nonselected birth cohort,13 and therefore the previous history of asthma could be confirmed from available data. Inhaled medication use for asthma or wheeze during the past year is described in Table II. None of the participants reported using oral medications for asthma during the past year. The majority of the asthmatic patients had a

Discussion

In this study, for the first time, we used the high-throughput 454 sequencing technology to obtain estimates of bacterial diversity in induced sputum. We demonstrate that, as was observed in 2 previous studies using invasive techniques to obtain airway samples, differences in bacterial community composition are associated with active asthma and Proteobacteria were more abundant in induced sputum of asthmatic than nonasthmatic subjects.

We found that samples from asthmatic patients have greater

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  • Cited by (0)

    Supported by Southwest Environmental Health Sciences (SWEHSC) training grant ES007901 (to P.R.M.). Part of this study was supported by National Heart, Lung, and Blood Institute grants HL 56177 and HL 14136 (to F.D.M. and A.L.W.) and SWEHSC grant ES006694 (to D.B.).

    Disclosure of potential conflict of interest: D. A. Stern has been supported by one or more grants from and/or has one or more grants pending with the National Institutes of Health (NIH). A. L. Wright has been supported by one or more grants from and/or has one or more grants pending with NIH, has received one or more payments for lecturing from or is on the speakers' bureau for the Association of American Medical Colleges and the University of Vermont, and has received one or more payments for the development of educational presentations for Association of American Medical Colleges. F. D. Martinez has been supported by one or more grants from CRS (HL56177), has consultancy arrangements with MedImmune, has received one or more grants from or has one or more grants pending with the NIH, has received one or more payments for lecturing from or is on the speakers' bureau for Abbott and Merck, and has received one or more payments for travel/accommodations/meeting expenses from Abbott and Merck. The rest of the authors declare that they have no relevant conflicts of interest.

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