Urinary Tract Infections in Kidney Transplant Recipients: An Observational Study at the Modena Transplant Center

Introduction Urinary tract infections (UTIs) are among the most frequent complications following kidney transplantation (KT). The aim of this study is to evaluate the 1-year incidence of UTI in kidney transplant recipients (KTRs), to identify predictors of UTI and recurrent UTI (rUTI), and to assess the impact of UTIs and/or rUTIs on graft-related outcomes. Materials and Methods We conducted a single-center, retrospective, observational study, including KTRs from November 2019 to September 2024 at the University Hospital of Modena. Data on UTIs in the first year and recurrences within 18 months were collected. Colonization was defined as presence of asymptomatic bacteriuria (AsB). UTI was defined as local and/or systemic symptoms compatible with UTI associated with a positive urine culture (>10⁵ CFU/mL). rUTI was defined as ≥ 3 episodes of UTI within 12 months or ≥ 2 episodes within 6 months by the same pathogen. Multivariate logistic regression was used to assess predictors. Kaplan-Meier curves evaluated the incidence of UTI and rejection. Results Among 170 patients, 94 (55.3%) had AsB, 50 (29.4%) developed at least one UTI, and 25 (14.7%) had recurrent episodes. The 1-year UTI incidence rate was 14.9 per 100 person-years (95% CI 11.3–19.7). Over a median follow-up of 25 months (IQR 9.6–59.4), 99 UTIs were reported, with 33.3% associated with bacteremia and 37.3% classified as recurrent. UTIs were more frequent in females compared to males (37.5% vs. 24.5%, p=0.053), and in patients with pre-transplant post-void residual. The most common pathogens were E. coli (42.5%, ESBL+ in 24%) and K. pneumoniae (45.5%, ESBL+ in 73%). Independent predictors of UTI included non-standard pre-KT prophylaxis, pre-stent removal colonization, and post-transplant urinary tract abnormalities. Predictors of rUTI were older age, UTI by an ESBL+ pathogen, and post-KT urinary tract complications. UTI was associated with higher rejection rates (22% vs 7.5%, p=0.009), especially when caused by ESBL+ pathogens (log-rank p<0.001). Conclusion UTIs affect one-third of KTRs within the first year post-transplant, with high recurrence rates. Infections by ESBL-producing K. pneumoniae were strongly associated with recurrence and rejection, underlining the need for tailored preventive strategies in high-risk patients.