Characterization of throat microbial flora in smokers with or without COPD

The study aimed to determine the relationship between throat microbiome and COPD. Sixty-five Chinese males (n=20, smokers without COPD; n=45 smokers with COPD) were included. Nonmetric multidimensional scaling indicated differences of microbiome between COPD and controls, but no difference was observed between COPD patients with differing degrees of lung function or disease severity. Rarefaction analyses suggested that operational taxonomic units (OTUs, species-level) richness decreased in COPD. The dominant taxa between COPD and controls were similar, but the proportions of taxonomic distribution were different. The dominant phyla were Bacteroidetes, Proteobacteria, Firmicutes and Fusobacteria. The dominant genera were Haemophilus, Leptotrichia, Porphyromonas, Fusobacterium, Veillonella, Streptococcus, Neisseria and Prevotella. Two dominant OTUs, otu3 (Veillonella_dispar) and otu4 (Streptococcus_unclassified), were identified. Otu3 and its father-level taxa, which were negatively correlated with predicted percent of forced expiratory volume in a second (FEV₁%pred), were increased in COPD. By contrast, otu4 and its father-level taxa, which were positively correlated with FEV₁%pred, were decreased in COPD. Otu4 also showed a slight potential as a COPD biomarker. To conclude, the throat microbiome was different between smokers with or without COPD, which is similar to findings from the lower respiratory tract. This study may strengthen our understanding of the relationship between microbiomes of different airway sites and COPD.