The Impact of Pre- Versus Post-Transplant Multidrug-Resistant Organism Colonization on Liver Transplant Outcomes: A Retrospective Cohort Study

Objectives: Infectious complications, particularly those caused by multidrug-resistant organisms (MDROs), remain a major cause of morbidity and mortality after liver transplantation (LT). While pre-transplant colonization is a recognized risk factor, its prognostic significance relative to post-transplant MDRO status remains unclear. This study evaluated the clinical impact of MDRO presence across the transplant timeline and identified predictors of post-transplant mortality and graft dysfunction. Methods: A retrospective cohort study of 110 adult LT recipients (2018–2024) was conducted at a tertiary center. Patients were stratified by pre-transplant ESBL/MDRO colonization or infection and by post-transplant MDRO status (modeled as a time-dependent exposure). Primary outcomes were one-year all-cause mortality and adverse graft outcomes. Results: Pre-transplant ESBL/MDRO presence (40% of recipients) was not associated with increased one-year mortality or adverse graft outcomes. Conversely, post-transplant MDRO status occurred in 44.5% of patients and was strongly associated with poor outcomes. Post-transplant MDRO colonization or infection was present in 88% (14/16) of non-survivors vs. 37% (35/94) of survivors (p < 0.001). One-year mortality was 47% (9/19) for post-transplant MDRO infection, 17% (5/30) for colonization alone, and 3% (2/61) with no post-transplant MDRO event. In a penalized time-dependent Cox model, post-transplant MDRO acquisition was independently associated with one-year mortality (HR 4.0, 95% CI 1.77–9.03; p < 0.001), confirmed by landmark analysis (HR 3.15, 95% CI 1.08–9.19), whereas pre-transplant status showed no association (p = 0.18). Conclusions: While pre-transplant status did not significantly impact one-year mortality in this cohort, post-transplant MDRO acquisition was independently associated with one-year mortality. Pre-transplant status should guide targeted prophylaxis, whereas the post-transplant period represents the critical window for infection prevention and antimicrobial stewardship interventions.