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

<bold>Introduction:</bold> Pulmonary dysbiosis has recently been highlighted as risk factor for mortality in lung transplant (LTX) recipients. Although pleural effusions frequently occur after LTX, the pleural microbiome remains unexplored in these patients. <bold>Methods:</bold> We analyzed bacterial diversity on a cohort of 185 pleural effusions of lung transplant recipients and non-transplant patients using a metabarcoding based approach targeting the 16S rRNA gene. Microbiome samples were controlled for contamination with sham controls and skin swabs. <bold>Results:</bold> Significant differences in bacterial alpha- and beta-diversity were found between early and late pleural effusions after LTX. Late pleural effusions after LTX showed a distinguished beta-diversity compared to non-transplant effusions. The pulmonary bacterial community structure of BAL samples correlated to the pleural bacterial diversity, which was associated with an exudative composition of the pleural effusion. <bold>Conclusions:</bold> We discovered an altered microbiome in pleural effusions of LTX recipients compared to non-transplant patients, that differed between early and late effusions after LTX. Given the correlation between the pulmonary and pleural microbiome, we propose a direct interaction between the microbiomes of both compartments.