Seasonal dynamics of airway microbiome in patients with COPD

COPD is one of the top three of death worldwide. Air pollution is a growing threat to public health due to increased mortality and morbidity worldwide, primarily triggering and exacerbating many respiratory diseases. The respiratory tract harbors specialized bacterial and fungal communities, the disturbance of which has been implicated in various respiratory diseases. The aim of this study was to investigate whether PM could induce a dysbiosis in the sputum microbiota. Patients with COPD were prospectively recruited from three university hospitals in the capital region of South Korea. The inclusion criteria of study participants were 1) ages 40–79 years, 2) forced expiratory volume in 1 s < 80% of the predicted value, 3) and presence of respiratory symptoms. After enrolment, patients were followed every three months at the respective hospitals for one year. We performed 16S rRNA sequencing using DNA isolated from sputum samples and analyzed dynamics of airway microbiota based on PM exposure levels and season. The baseline outdoor, indoor, and estimated individual exposure level of PM2.5 were 14.8, 12.1, and 12.8 μg/m³, respectively. We found that PM-low exposure group has higher α-diversity in spring compared to PM-high exposure group. The sputum samples in low exposure group were significantly more abundant with 7 bacterial species. In addition, bacterial α-diversity in summer is significantly higher than that in spring. We also found that PCoA analysis of individual sputum microbiota showed a significant difference between low and high exposure on PM2.5 over a year in moderate COPD patients. Our results have suggested that airway microbiomes could covary with PM exposure according to seasonal trends.