ABSTRACT
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.
Subject(s)
Graft Rejection/microbiology , Lung Transplantation/adverse effects , Lung/microbiology , Microbiota/immunology , Pneumonia, Bacterial/microbiology , Adult , Allografts/immunology , Allografts/microbiology , Bacteria/genetics , Bacteria/immunology , Bacteria/isolation & purification , Bacteria/pathogenicity , Bacterial Load/immunology , Bacteriological Techniques , Bronchoalveolar Lavage Fluid/microbiology , Bronchoscopy , DNA, Bacterial/isolation & purification , Female , Graft Rejection/diagnosis , Graft Rejection/immunology , Humans , Immune Tolerance , Longitudinal Studies , Lung/immunology , Male , Metagenomics , Microbiota/genetics , Middle Aged , Pneumonia, Bacterial/diagnosis , Pneumonia, Bacterial/immunology , Prospective Studies , RNA, Ribosomal, 16S/geneticsABSTRACT
OBJECTIVES: A lung retransplant has been shown to be a valid option in selected patients with chronic lung allograft dysfunction (CLAD). However, a subgroup of patients may require, in addition to invasive mechanical ventilation, extracorporeal membrane oxygenation (ECMO) as a bridge to a retransplant. Overall and CLAD-free survival after ECMO-bridged retransplants are compared to first transplants with and without bridging ECMO and to retransplants without bridging ECMO. METHODS: We reported a retrospective, single-institution experience based on a prospective data set of all patients undergoing lung transplants between January 2004 and December 2016 with a mean follow-up of 51 ± 41 months. RESULTS: A total of 230 patients (96 men, 134 women, mean age 47.3 years) had lung transplants: 200 had first transplants without bridging ECMO; 13 had first transplants with bridging ECMO; 11 had retransplants without bridging ECMO; and 6 had retransplants with bridging ECMO. The 3- and 5-year survival rates were 81%/76%, 68%/68%, 69%/46% and 50%/25%, respectively. There was no significant difference in overall survival between those who had first transplants with and without bridging ECMO or retransplants without bridging ECMO. In contrast, patients undergoing ECMO-bridged retransplants had a significantly lower overall survival rate than those with a first transplant without bridging ECMO (P = 0.007). In addition, the post-transplant CLAD-free survival curves varied significantly among the 4 treatment groups (P = 0.041), paralleling overall survival. CONCLUSIONS: Patients requiring ECMO as a bridge to a retransplant had lower overall and CLAD-free survival rates compared to those who had a first transplant with and without bridging ECMO and a retransplant without bridging ECMO.
