Bacterial biogeography of adult airways in atopic asthma

Abstract

BackgroundPerturbations to the composition and function of bronchial bacterial communities appear to contribute to the pathophysiology of asthma. Unraveling the nature and mechanisms of these complex associations will require large longitudinal studies, for which bronchoscopy is poorly suited. Studies of samples obtained by sputum induction and nasopharyngeal brushing or lavage have also reported asthma-associated microbiota characteristics. It remains unknown, however, whether the microbiota detected in these less-invasive sample types reflect the composition of bronchial microbiota in asthma.ResultsBacterial microbiota in paired protected bronchial brushings (BB; n = 45), induced sputum (IS; n = 45), oral wash (OW; n = 45), and nasal brushings (NB; n = 27) from adults with mild atopic asthma (AA), atopy without asthma (ANA), and healthy controls (HC) were profiled using 16S rRNA gene sequencing. Though microbiota composition varied with sample type (p < 0.001), compositional similarity was greatest for BB-IS, particularly in AAs and ANAs. The abundance of genera detected in BB correlated with those detected in IS and OW (r median [IQR] 0.869 [0.748–0.942] and 0.822 [0.687–0.909] respectively), but not with those in NB (r = 0.004 [− 0.003–0.011]). The number of taxa shared between IS-BB and NB-BB was greater in AAs than in HCs (p < 0.05) and included taxa previously associated with asthma.Of the genera abundant in NB, only Moraxella correlated positively with abundance in BB; specific members of this genus were shared between the two compartments only in AAs. Relative abundance of Moraxella in NB of AAs correlated negatively with that of Corynebacterium but positively with markers of eosinophilic inflammation in the blood and BAL fluid. The genus, Corynebacterium, trended to dominate all NB samples of HCs but only half of AAs (p = 0.07), in whom abundance of this genus was negatively associated with markers of eosinophilic inflammation.ConclusionsInduced sputum is superior to nasal brush or oral wash for assessing bronchial microbiota composition in asthmatic adults. Although compositionally similar to the bronchial microbiota, the microbiota in induced sputum are distinct, reflecting enrichment of oral bacteria. Specific bacterial genera are shared between the nasal and the bronchial mucosa which are associated with markers of systemic and bronchial inflammation.Electronic supplementary materialThe online version of this article (10.1186/s40168-018-0487-3) contains supplementary material, which is available to authorized users.

Environmental Exposures Influence Nasal Microbiome Composition in a Longitudinal Study of Division I Collegiate Athletes

“…It’s unclear whether athletes choose an athletic career in the pool because of underlying airway issues, such as asthma, or whether exposure to chlorine and byproducts precedes disease. We hypothesized that altered nasal microbiome composition may contribute to airway disease, as has been previously described in patients with AR and asthma [9,20,21]. While we have not mechanistically demonstrated this in the current study, our results suggest that elite athletes exposed to chlorinated water have altered microbial composition.…”

Characterization and Analysis of The Nasal Microbiota and Plasmatic Extracellular Vesicles in Allergic Rhinitis: A Case-Control Study

“…Indeed, the relative abundance of nasal Moraxella genus was positively correlated with systemic and airway eosinophil counts, tumor-necrosis factor alpha (TNF-α) and interleukin (IL-)7, suggesting a possible pro-in ammatory role of this genus in the bNM. On the contrary, the Corynebacterium genus, found in greater abundance in the analysed HS group, has been negatively correlated with atopic markers such as IL-6, IL-7 and IL-21 as well as with total eosinophil counts [54]. In agreement with our nding, it is known that exaggerated immune response along with a dysfunctional immune barrier and an in amed mucosal epithelium can promote the overgrowth of certain microorganisms and dysbiosis in AR, asthmatic and CR patients [55].…”

The crosstalk between microbiome and asthma: Exploring associations and challenges

“…In another study comparing bacterial composition in bronchial aspirates and bronchial brushings in 13 adults with severe asthma, the composition of the microbiota in the bronchial brushings showed a specific pattern that was not represented in bronchial aspirates . Induced sputum was found to be more compositionally similar to bronchial brushings than oral washes or nasal brushings in adult atopic asthmatics (n = 22) . A study conducted in 60 individuals comparing stool samples with rectal swabs found that certain bacterial taxa are highly specific to the sample site, while other taxa can be found in both sample types and are specific for the individual …”

“…Since many different sampling compartments and methods are currently used, obtained results are difficult to compare. For example, a study conducted in 39 asthmatics and 19 healthy controls revealed that statistically significant differences in bacterial α‐diversity (diversity in individual site or sample) and β‐diversity (intervariability, between sites or samples) were found between bronchial brushings and bronchoalveolar lavage (BAL) fluid within individuals for both asthmatics and control groups .…”