Composition of airway bacterial community correlates with chest HRCT in adults with bronchiectasis

Abstract

Background and objective In bronchiectasis (BE) not caused by cystic fibrosis, chronic, polymicrobial airway infection contributes to the underlying pathogenesis of disease. There is little information on whether bacterial community composition relates to clinical status. We determined the relationship between bacterial community composition, chest high‐resolution computed tomography (HRCT) scores and clinical markers in BE. Methods A subgroup of BE patients from a previous cross‐sectional study were analysed. Spontaneously expectorated sputum was analysed using culture‐independent sequencing on the Roche 454‐FLX platform covering the V1–V3 region of the 16S rRNA marker gene. Chest HRCT scans, multiple breath washout, spirometry and blood inflammatory markers were collected. Spearman's rank (r) correlation coefficient was used to assess relationships. Results Data from 21 patients were analysed (mean (SD) age: 64.0 (7.7); female : male 14:7; mean (SD) forced expiratory volume in 1 s (FEV1): 76.5 (17.2)). All bacterial community composition metrics (bacterial richness, diversity, evenness and dominance) correlated with percentage BE score, with more severe HRCT abnormality relating to lower bacterial richness, evenness and diversity (range r = −0.47 to −0.66; P < 0.05). Inflammation (C‐reactive protein and white cell count) was greater in patients with lower diversity and richness (range r = −0.44 to −0.47; P < 0.05). Bacterial community characteristics did not correlate with lung function. Conclusion This is the first study to indicate a relationship between bacterial community characteristics by 16S rRNA marker gene sequencing, structural damage as determined by chest HRCT and clinical measures in BE. The association between loss of diversity and chest HRCT severity suggests that bacterial dominance with pathogenic bacteria may contribute to disease pathology.

Lung clearance index in healthy volunteers, measured using a novel portable system with a closed circuit wash-in

“…The data analysis package was developed in-house, and is not the same as that shipped with the Innocor device. However it has been developed from that deployed in multiple previous studies [4,37], including the CF gene therapy trial [25], and updated to incorporate consensus recommendations [1]. It has not been possible to compare LCI using our data analysis package with that of the Innocor system due to differences in flow-gas delay correction.…”

The airway microbiome in COPD, bronchiectasis and bronchiectasis‐COPD overlap

“…15,16 Positive correlation is further reported between radiological severity (using chest high-resolution computed tomography (HRCT)) and decreased diversity although studies remain limited by sample size. 72 The role, if any, of the airway microbiome in bronchiectasis exacerbations remains poorly understood. The microbiome in bronchiectasis exacerbations is highly individualised and exacerbations are complex events not solely explained by bacterial overgrowth but include interaction with the surrounding environment and/or co-infection.…”

The microbiome in bronchiectasis: Cutting a lung story short

“…present a study looking into the relationship between airway bacterial community composition and bronchiectasis severity. The former was measured in sputum, using 16S rRNA sequencing, and conventional analysis pipelines were used to determine bacterial richness, diversity, evenness and dominance . Clinical status was assessed using chest high‐resolution computed tomography (HRCT) scores, forced expiratory volume in 1 s (FEV 1 ) % predicted, forced expiratory flow at 25–75% of forced vital capacity (FEF 25–75 %) predicted, lung clearance index and blood inflammatory markers.…”

“…The former was measured in sputum, using 16S rRNA sequencing, and conventional analysis pipelines were used to determine bacterial richness, diversity, evenness and dominance. 8 Clinical status was assessed using chest high-resolution computed tomography (HRCT) scores, forced expiratory volume in 1 s (FEV 1 ) % predicted, forced expiratory flow at 25-75% of forced vital capacity (FEF 25-75 %) predicted, lung clearance index and blood inflammatory markers. While this study is by no means the largest microbiome study in bronchiectasis, it has the broadest assessment of different measures of disease extent and severity to date.…”