Relationship between the respiratory microbiome and the severity of airflow limitation, history of exacerbations and circulating eosinophils in COPD patients

BackgroundThe respiratory microbiome is altered in COPD patients but its relationship with core components of the disease, such as the severity of airflow limitation, the frequency of exacerbations or the circulating levels of eosinophils, is unclear.MethodsCross-sectional study comprising 72 clinically stable COPD patients (mean age 68 [SD 7.9] years; FEV1 48.7 [SD 20.1]% of reference) who provided spontaneous sputum samples for 16S rRNA gene amplification and sequencing. The microbiome composition was analysed with QIIME.ResultsWe observed that: (1) more severe airflow limitation was associated with reduced relative abundance (RA) of Treponema and an increase in Pseudomonas; (2) patients with 2 exacerbations the previous year showed a significantly different bacterial community with respect to non-exacerbators (p=0.014), with changes in 13 genera, including an increase of Pseudomonas, and finally, (3) peripheral eosinophils levels 2% were associated with more diverse microbiome [Chao1 224.51 (74.88) vs 277.39 (78.92) p=0.006; Shannon 3.94 (1.05) vs 4.54 (1.06) p=0.020], and a significant increase in the RAs of 20 genera.ConclusionThe respiratory microbiome in clinically stable COPD patients varies significantly according to the severity of airflow limitation, previous history of exacerbations and circulating eosinophils levels.
This study was funded by FIS PI15/00167 and PI15/02042 from Instituto de Salud Carlos III (ISCIII), SAF 2014-54371 (FEDER) from Ministerio de Economia y Competitividad, Sociedad Espanola de Neumologia y Cirugia Toracica (SEPAR), Laboratorios Menarini S. A, Fundacio Pla Armengol and Centro de Investigacion Biomedica en Red de Enfermedades Respiratorias (CIBERES). CIBERES is an initiative of the ISCIII.; This work was also supported by grants from Agencia de Gestio d'Ajuts Universitaris i de Recerca-Generalitat de Catalunya (2017 GRC-716).