Comparison of the upper and lower airway microbiota in early postoperative lung transplant recipients.

The lung dysbiosis is associated with the development of transplant complications, and aberrant upper respiratory tract microbiome may increase the risk of infection after lung transplantation, suggesting a close relationship between upper and lower respiratory tract microbiota in lung transplant recipients (LTRs). Thirty-four paired respiratory samples were collected from 17 early postoperative LTRs, including 17 nasal swab (NS) and 17 bronchoalveolar lavage fluid (BALF). 16S rRNA sequencing was performed, the microbial diversity and community composition of airway microbiome were analyzed. The airway microbiota signature differs between upper and lower respiratory tract in early postoperative LTRs in alpha diversity, beta diversity, 16S rRNA reads and microbial community composition. Several differential bacterial genera were identified between different sampling sites, with Corynebacterium, Acinetobacter, Pseudomonas, Staphylococcus, Propionibacterium and Planococcaceae sp. enriched in NS samples, and Ralstonia, Stenotrophomonas, Chryseobacterium, Pedobacter, Enterococcus, Bacillus, Variovorax and Xanthomonadaceae sp. increased in BALF samples. Dissimilarity between paired NS and BALF (intra-subject) samples was greater than inter-subject samples of both NS and BALF, indicating that the difference of airway microbiota was significantly affected by sampling sites than by sampling individuals. The microbial difference of early postoperative LTRs between upper and lower respiratory tract mainly comes from sampling sites instead of sampling individuals. Microbial studies using nasal samples as substitutes for lower respiratory tract should be interpreted with caution.