Oral microbiome in COPD patients: association with lung function and impacts of smoking and inhaled corticosteroids

Background The aim of our study was to describe the characteristics of oral microbiome in patients with chronic obstructive pulmonary disease (COPD) with different pulmonary function grades, and to investigate the impact of smoking and inhaled corticosteroids (ICS) on the oral microbiome in patients with various lung function impairments. Methods Pyrosequencing of polymerase chain reaction-amplified 16s rDNA genes was used to investigate the oral microbiome. COPD was diagnosed based on the Global Initiative for Chronic Obstructive Lung Disease (GOLD) Guidelines 2021. Results Bacterial richness and diversity increased in GOLD2-4 patients, and the beta-diversity analysis indicated differences between GOLD2-4 groups and CTRL-GOLD1 groups. Veillonella, Actinomyces, Escherichia-Shigella and Lactobacillus varies with different lung functions and there were different dominant strains in different groups, respectively. Functional genes of oral microbiome in GOLD2-4 patients also unfolded considerable discrepancy compared to CTRL. Smoking increased the abundance of Prevotella_7, Veillonella, Leptotrichia and Prevotella in GOLD 2–4 patients as well as the abundance of sixteen KEGG pathways. ICS treatment increased the diversity of the oral microbiome, and Prevotella and Porphyromonas were biomarkers found in the ICS group. Conclusions As lung function declined, the diversity, structure, distribution and signature of the oral microbiome changed, and the oral microbiomes of patients with different lung function had unique characteristics. Smoking and ICS affected the oral microbiome of COPD patients. Taken together, our findings may not only partially explain the mechanism of onset and development of COPD from perspective of the oral microbiome and its functional genes, but also provide an in-depth understanding of biomarker bacteria for COPD grades.