Comparative analysis of the sputum microbiota in different COPD clinical states

Chronic obstructive pulmonary disease (COPD) is a well-known respiratory illness. COPD patients oscillate between a stable state and an exacerbated state that leads to disease deterioration. Studies suggest that respiratory microbiome dysbiosis plays a vital role in COPD pathogenesis. However, the exact microbial composition among different clinical states of COPD is still elusive. To determine and compare the respiratory microbiota composition in different COPD clinical states, namely, the stable state (S-COPD) and the acute exacerbated state (AE-COPD). In this prospective study, 74 samples were collected from COPD patients. The sputum microbiota was analyzed via 16 S rRNA gene sequencing, and only 35 samples were included due to bad reads or not in accordance with inclusion criteria: S-COPD patients (n = 18), and AE-COPD patients (n = 17). Bioinformatics analysis was used to determine changes in the microbiota among the comparison groups. The most abundant phyla among all the samples were Proteobacteria, Fusobacteria, Firmicutes, and Actinobacteria, with Paracoccus, Streptomyces Leptotrichia Fusobacterium and Ruminococcaceae being the most prevalent genera. Dissimilarity in abundance across the studied COPD states was observed, with significantly greater abundance of Proteobacteria and Fusobacteria in S-COPD patients and greater abundance of Firmicutes in AE-COPD patients at the phylum level. At the genus level, Paracoccus, Fusobacterium, Streptococcus, Haemophilus, and Moraxella were significantly different between the two groups and were more prevalent in S-COPD, whereas Cellulosilyticum, Streptomyces, Leptotrichia, Ruminococcaceae_UCG_014, and Atopobium were more prevalent in exacerbated individuals. Alpha diversity revealed greater diversity in stable versus exacerbated patients, and a PCoA plot of Bray‒Curtis and weighted UniFrac distances revealed that stable patients were highly clustered, whereas exacerbated patients were more disseminated. At the genus level, LEfSe analysis revealed the dominance of Cellulosilytic, Liptotrichia, and Streptomyces in the AE-COPD group, whereas the S-COPD group microbiome was dominated by the genera Paracoccus, Fusobacterium, Streptococcus Haemophilus, and Moraxella (p < 0.05). The results of the present study suggest that COPD patients have unique microbial profiles that differ across different states, with increased abundances of Proteobacteria, chiefly Paracoccus. These findings need more research to clarify the definite role of microbiome dysbiosis in COPD pathogenesis.