Chasing Shadows? Antibiotic Treatment for Asymptomatic Bacteriuria in the First 30 Days Post-Kidney Transplant

Abstract

Asymptomatic bacteriuria (ASB) is common after kidney transplantation, but the benefit of antibiotic treatment during the immediate post-transplant period remains uncertain. We evaluated whether treatment of ASB within the first month after kidney transplantation was associated with improved rejection and infectious outcomes. We conducted a retrospective cohort study of adults who received a kidney transplant at the University of Washington Medical Center from January 2017 through April 2025 and had at least one ASB episode within 30 days after transplantation. The primary exposure was antibiotic treatment of ASB. The primary outcome was biopsy-proven rejection within 1 year. Secondary outcomes included urinary tract infection (UTI) within 2 weeks of ASB, multidrug-resistant organism (MDRO) isolation and Clostridioides difficile infection within 1 year of transplant. Cox proportional hazards and logistic regression models were used for crude and adjusted analyses. Additional sensitivity analyses including alternative multivariate models, propensity score adjustment, and inverse probability of treatment weighting (IPTW) were conducted to assess the robustness of the findings. Among 1,851 kidney transplant recipients reviewed, 359 patients had at least one ASB episode within 30 days, comprising 620 ASB episodes. Seventy-two patients with 112 ASB episodes received treatment whereas 287 with 508 ASB episodes did not receive treatment. Conventional multivariate models demonstrated a signal toward increased biopsy-proven rejection risk within 1 year in treated ASB group (adjusted HR, 2.39; 95% CI, 0.88–6.47; p-value = 0.09), although this association was attenuated in propensity-adjusted (HR, 1.26 [95% CI, 0.44–3.56]; p-value = 0.67) and IPTW analyses (HR, 1.03 [95% CI, 0.34–3.19]; p=0.95). Treatment was associated with higher odds of UTI within 2 weeks after ASB (adjusted OR, 6.5 [95% CI, 1.5–33.4]; p-value = 0.02). MDRO isolation and Clostridioides difficile infection within 1 year were more frequent among treated patients, although the differences did not reach statistical significance. Antibiotic treatment of ASB during the first month after kidney transplantation was not associated with improved clinical outcomes and may increase downstream infectious and antimicrobial resistance-related complications. These findings support further evaluation of antimicrobial stewardship approaches for early post-transplant ASB management.