The Lung Microbiome Predicts Mortality and Response to Azithromycin in Lung Transplant Patients with Chronic Rejection.

Combs MP, Luth JE, Falkowski NR, Wheeler DS, Walker NM, Erb-Downward JR, Wakeam E, Sjoding MW, Dunlap DG, Admon AJ, Dickson RP, Lama VN. The Lung Microbiome Predicts Mortality and Response to Azithromycin in Lung Transplant Patients with Chronic Rejection. American journal of respiratory and critical care medicine. 2024 Jan 25.

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Abstract:

RATIONALE: Chronic lung allograft dysfunction (CLAD) is the leading cause of death following lung transplant, and azithromycin has variable efficacy in CLAD. The lung microbiome is a risk factor for developing CLAD, but the relationship between lung dysbiosis, pulmonary inflammation, and allograft dysfunction remains poorly understood. Whether lung microbiota predict outcomes or modify treatment response CLAD is unknown. OBJECTIVES: To determine whether lung microbiota predict post-CLAD outcomes and clinical response to azithromycin. METHODS: Retrospective cohort study using acellular bronchoalveolar lavage (BAL) fluid prospectively collected from lung transplant recipients within 90 days of CLAD onset. Lung microbiota were characterized using 16S rRNA gene sequencing and ddPCR. In two additional cohorts, causal relationships of dysbiosis and inflammation were evaluated by comparing lung microbiota with CLAD-associated cytokines and measuring growth in sterilized BAL fluid. MEASUREMENTS AND MAIN RESULTS: Patients with higher bacterial burden had shorter post-CLAD survival, independent of CLAD phenotype, azithromycin treatment, and relevant covariates. Azithromycin treatment improved survival in patients with high bacterial burden, but had negligible impact on patients with low or moderate burden. Lung bacterial burden was positively associated with CLAD-associated cytokines, and was augmented in BAL fluid from transplant recipients with CLAD. CONCLUSIONS: In lung transplant patients with chronic rejection, increased lung bacterial burden is an independent risk factor for mortality and predicts clinical response to azithromycin. Lung bacterial dysbiosis is associated with alveolar inflammation and may be promoted by underlying lung allograft dysfunction.