BACKGROUND: Despite advances in immunosuppression and perioperative care, lung transplantation (LuTX) outcome continues to be limited by allograft rejection and infectious complications. Given the allograft's direct exposure to the environment, peri-transplant microbial presence and dynamics may critically shape outcomes, yet its impact remains incompletely understood. This study aimed to evaluate peri-transplant airway microbiological findings in lung transplant recipients and determine their associations with acute cellular rejection (ACR), chronic lung allograft dysfunction (CLAD), and survival. METHODS: We retrospectively analyzed 345 LuTX recipients treated between 2014 and 2019 with follow-up through 2024. Standardized microbiological sampling was performed pre-, intra- and postoperatively. Associations with ACR, CLAD and survival were evaluated. RESULTS: Candida species (spp.) (22.6% and 18.3%, respectively) and Pseudomonas aeruginosa (10.7% and 7.2%) were most frequently detected in pre- and postoperative sputum samples. Donor lungs showed positive microbial samples in 62.3% of cases, predominantly with Candida spp. (31.3%) and Staphylococcus spp. (26.1%). Multivariate analysis identified donor-derived Escherichia coli as an independent predictor of ACR (P=0.01; odds ratio 3.2), CLAD [P=0.03; hazard ratio (HR) 2.6] and impaired survival (P<0.001; HR 3.2). Furthermore, donor-derived Achromobacter spp. (P=0.01; HR 13.6) and postoperative deep airway Candida detection (P=0.045; HR 1.9) predicted mortality. While Klebsiella was associated with adverse outcomes in univariate analysis, this did not remain significant after adjustment. CONCLUSIONS: Peri-transplant airway microbiota are significantly associated with graft rejection and survival after LuTX. Donor-derived E. coli and Achromobacter spp., as well as postoperative Candida detection, emerged as robust predictors of poor outcome. Systematic microbiological surveillance and tailored prophylaxis are essential to mitigate microbial-driven allograft dysfunction and improve long-term survival.
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