A prevalent and culturable microbiota links ecological balance to clinical stability of the human lung after transplantation

There is accumulating evidence that the lower airway microbiota impacts lung health. However, the link between microbial community composition and lung homeostasis remains elusive. We combine amplicon sequencing and bacterial culturing to characterize the viable bacterial community in 234 longitudinal bronchoalveolar lavage samples from 64 lung transplant recipients and establish links to viral loads, host gene expression, lung function, and transplant health. We find that the lung microbiota post-transplant can be categorized into four distinct compositional states, 'pneumotypes'. The predominant 'balanced' pneumotype is characterized by a diverse bacterial community with moderate viral loads, and host gene expression profiles suggesting immune tolerance. The other three pneumotypes are characterized by being either microbiota-depleted, or dominated by potential pathogens, and are linked to increased immune activity, lower respiratory function, and increased risks of infection and rejection. Collectively, our findings establish a link between the lung microbial ecosystem, human lung function, and clinical stability post-transplant. Here, the authors combine 16S rRNA sequencing, culture and bioinformatics to profile the microbiome in 234 serial bronchoalveolar lavage samples from 64 lung transplant recipients collected over 49-months and identify distinct compositional states, termed pneumotypes, linked to current health status, and establish a collection of primary lung bacterial isolates, LuMiCol.

Automated summary

This study examined the viable bacterial community in bronchoalveolar lavage samples from 64 lung transplant recipients and identified four distinct compositional states, called "pneumotypes," which were associated with immune activity, lung function, and risks of infection and rejection. The findings highlight the link between the lung microbial ecosystem, human lung function, and clinical stability post-transplant.