Enrichment of oral anaerobic bacteria in the lung microbiota of individuals with normal lung function

Abstract

The oral microbiota is increasingly considered a source of microorganisms for the entire body. This study collected saliva before bronchoscopy and bronchial fluid during bronchoscopy using a protected specimen brush from 44 individuals with normal lung function and no evidence of lung or airway infection to examine the microbial link between the oral and lung microbiota. The bacterial composition of each sample was determined using PacBio single-molecule long-read sequencing of the full-length 16S ribosomal RNA gene and amplicon sequence variant (ASV) analysis. The loads of total bacteria and Porphyromonas gingivalis were determined by quantitative polymerase chain reaction analysis. The total bacterial load significantly correlated between salivary and lung microbiota, and salivary ASVs accounted for 64.8% (median) of the lung microbiota in each participant. In the lung microbiota, Porphyromonas endodontalis, Prevotella salivae, Alloprevotella tannerae, Prevotella oris, Fusobacterium nucleatum, and P. gingivalis were significantly more abundant than in the salivary microbiota. The P. gingivalis load also showed a significant correlation between salivary and lung microbiota, and the lung load was significantly higher in individuals with P. gingivalis in their saliva than in those without it. These results suggest that the salivary microbiota contributes to the formation of lung microbiota, and that obligate anaerobic bacteria derived from the oral cavity are enriched in the lungs.