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Background. Lung transplant patients are vulnerable to various forms of allograft injury, whether from acute rejection (AR) (encompassing acute cellular rejection [ACR] and antibody-mediated rejection [AMR]), chronic lung allograft dysfunction (CLAD), or infection (INFXN). Previous research indicates that donor-derived cell-free DNA (dd-cfDNA) is a promising noninvasive biomarker for the detection of AR and allograft injury. Our aim was to validate a clinical plasma dd-cfDNA assay for detection of AR and other allograft injury and to confirm and expand on dd-cfDNA and allograft injury associations observed in previous studies. Methods. We measured dd-cfDNA fraction using a novel single-nucleotide polymorphism-based assay in prospectively collected plasma samples paired with clinical-pathologic diagnoses. dd-cfDNA fraction was compared across clinical-pathologic cohorts: stable, ACR, AMR, isolated lymphocytic bronchiolitis, CLAD/neutrophilic-responsive allograft dysfunction (NRAD), and INFXN. Performance characteristics were calculated for AR and combined allograft injury (AR + CLAD/NRAD + INFXN) versus the stable cohort. Results. The study included 195 samples from 103 patients. Median dd-cfDNA fraction was significantly higher for ACR (1.43%, interquartile range [IQR]: 0.67%–2.32%, P = 5 × 10−6), AMR (2.50%, IQR: 2.06%–3.79%, P = 2 × 10−5), INFXN (0.74%, IQR: 0.46%–1.38%, P = 0.02), and CLAD/NRAD (1.60%, IQR: 0.57%–2.60%, P = 1.4 × 10−4) versus the stable cohort. Area under the receiver operator characteristic curve for AR versus stable was 0.91 (95% confidence interval [CI]: 0.83-0.98). Using a ≥1% dd-cfDNA fraction threshold, sensitivity for AR was 89.1% (95% CI: 76.2%-100.0%), specificity 82.9% (95% CI: 73.3%-92.4%), positive predictive value, 51.9% (95% CI: 37.5%-66.3%), and negative predictive value, 97.3% (95% CI: 94.3%-100%). For combined allograft injury area under the receiver operator characteristic curve was 0.76 (95% CI: 0.66-0.85), sensitivity 59.9% (95% CI: 46.0%-73.9%), specificity 83.9% (95% CI: 74.1%-93.7%), positive predictive value, 43.6% (95% CI: 27.6%-59.6%), and negative predictive value, 91.0% (95% CI: 87.9%-94.0%). Conclusions. These results indicate that our dd-cfDNA assay detects AR and other allograft injury. dd-cfDNA monitoring, accompanied by standard clinical assessments, represents a valuable precision tool to support lung transplant health and is appropriate for further assessment in a prospective randomized-controlled study.

Lactobacilli are rod shaped gram positive bacteria that naturally colonize the human gastrointestinal and genitourinary tracts and occasionally cause disease in humans. Lactobacillus infections are found in patients who are immunocompromized or have severe comorbidities. We report Lactobacillus endocarditis in a 17-year-old adolescent girl with cardiac prosthetic material following surgical correction for complex cyanotic congenital heart disease. Accurate identification of the organism can be delayed. Despite in vivo susceptibility to vancomycin, our patient clinically failed vancomycin therapy but ultimately responded to a six-week course of penicillin, in addition to a 4-week course of clindamycin and gentamicin. She recovered without the need for surgical intervention and has been symptom free for one year. Upon review of the literature, we found that Lactobacillus endocarditis has not been reported in a pediatric patient with complex cyanotic congenital heart disease.