The pleural microbiome in lung transplant recipients and non-transplant patients

Introduction: Pleural effusions of unknown etiology frequently occur in lung transplant (LTX) recipients and are associated with reduced survival. The pulmonary microbiome is increasingly recognized in LTX recipients. The pleural microbiome however, has not yet been investigated and several factors, e. g. open chest surgery, severe immunosuppression and long-term macrolide therapy might alter the pleural microbiome in LTX recipients. Methods: We analyzed a cohort of 52 pleural effusions of lung transplant recipients and non-transplant patients and 14 matched bronchoalveolar lavage samples of lung transplant recipients by 16S rRNA sequencing. Results: Significant differences in pleural cytology as well as alpha- and beta-diversity were found between early and late pleural effusions after LTX. Late pleural effusions after LTX showed a trend towards a higher alpha- and beta-diversity compared to non-transplant effusions. The pulmonary microbiome of BAL samples showed a correlation to the pleural microbiome, which was associated with an exudative composition of the pleural effusion. Conclusions: Lung transplantation and time after lung transplantation seem to affect the pleural microbiome. As the pulmonary and pleural microbiome directly correlated, we suggest a communication of the microbiome of both compartments.