Characteristics of upper and lower respiratory tract microbiota after lung transplantation.

BACKGROUND

The composition and characteristics of airway microbiota offer critical insights for clinical decision-making. Current research on chronic lung diseases shows differences in the composition and characteristics of upper and lower respiratory tract microbiota compared with healthy individuals. However, the temporal changes of these microbial communities in lung transplant recipients remain poorly characterized.

METHODS

This is a longitudinal prospective study. Respiratory specimens were collected regularly from lung transplant recipients for testing and analysis. A total of 150 bronchoalveolar lavage fluid (BALF) samples, 150 throat swab samples, 51 sputum samples, and 36 lung tissue samples were collected from the recipients, at 7 days, 14 days, 1 month, 2 months, 3 months, and 6 months post-transplant for 16S rRNA gene sequencing and analysis.

RESULTS

Our study showed that there were significant differences in α-diversity and β-diversity among lung tissue, throat swab, and sputum samples, although α-diversity did not show a significant difference between lung tissue and BALF. Most amplicon sequence variants (ASVs) belonged to the families Enterobacteriaceae, Pseudomonadaceae, and Stenotrophomonas in BALF, while most ASVs belonged to the genera Streptococcus, Pseudomonadaceae, and Stenotrophomonas in sputum samples. Regarding dynamic changes, Corynebacterium and Staphylococcus were more prevalent in the early post-operative period but gradually decreased by 7 days post-operatively, while the common microbiota found in healthy populations based on literature became the most abundant ASVs at 6 months post-operatively in our study participants. Pseudomonadaceae and Stenotrophomonas contributed to the similarity in the composition of upper and lower respiratory microbiota.

CONCLUSIONS

This study demonstrates that lung transplant recipients exhibit unique characteristics in their upper and lower respiratory tract microbiota, which are distinct ecological profiles, and both undergo significant changes within 6 months post-operatively. The similarity between upper and lower respiratory tract microbiota is associated with microbial diversity and taxonomic dominance.

CLINICAL TRIAL

The clinical trial was registered at Chinese Clinical Trial Registry (ChiCTR2200056908) in February 2022.