Extended-spectrum beta-lactamase producing pathogens as key drivers of recurrent urinary tract infections and rejection after kidney transplantation: a five-year single-centre study

Abstract Background This study aimed to evaluate the 1-year incidence of Urinary tract infections (UTI) in kidney transplant recipients (KTR), and to identify predictors of UTI and recurrent UTI (rUTI). Materials and Methods We conducted a retrospective, observational study including KTR from November 2019 to September 2024 at the University Hospital of Modena. Data on UTI in the first year and recurrences within 18 months were collected. Colonization, UTI, and rUTI were defined as follows: presence of asymptomatic bacteriuria (AsB); symptomatic UTI with positive culture (10⁵ CFU/mL); and recurrence by the same pathogen, respectively. Multivariate logistic regression was used to assess predictors. Kaplan-Meier curves evaluated incidence of UTI according to pre-KT and pre-stent removal prophylaxis and incidence of rejection. Results Among 170 KTR, over a median follow-up of 25 months (IQR 9.6–59.4), 99 UTIs occurred in 50 (29.4%) patients, of which 33.3% were associated with bacteraemia and 37.3% were classified as recurrent. The most common pathogens were Escherichia coli (42.5%, ESBL+ in 24%) and Klebsiella pneumoniae (45.5%, ESBL+ in 73%). The 1-year UTI incidence rate was 14.9 per 100 person-year (95% CI 11.3–19.7). UTI were less frequent in patients receiving amoxicillin/clavulanate pre-KT prophylaxis (11.8%, versus 26%, P= 0.024), while targeted prophylaxis based on pre-stent removal urine culture showed no protective effect (38.7% versus 40.5%, P= 0.938) (Figure 1a and b). In multivariate analysis, confirmed risk factors of UTI were female sex, positive urine donor and recipient pre-transplant culture, AsB pre-stent removal and post-transplant urinary tract abnormalities; predictors of rUTI were older age, ESBL+ colonization, and post-KT urinary tract complications (Table 1). UTI led to higher rejection rates (22% versus 7.5% with no UTI, P= 0.009), especially when caused by ESBL+ pathogens (P 0.001) (Figure 2). Conclusions UTI affect one-third of KTR within the first-year post-transplant, with high recurrence. Main risk factors included positive donor or recipient pre-transplant urine cultures, stent colonization, and post-transplant urinary tract abnormalities. Pre-transplant prophylaxis with amoxicillin/clavulanate was associated with lower UTI incidence, whereas targeted prophylaxis pre-stent removal did not confer protection. ESBL- producing pathogens were an independent predictor of recurrence and rejection, highlighting the need for tailored preventive strategies in high-risk recipients.Figure 1.Post-KT urinary tract infections occurrence according to pre-transplant antibiotic prophylaxis (a) and targeted pre-stent removal prophylaxis (b). Figure 2.Rejection occurrence. Table 1.Risk factors associated to UTI and recurrent UTIPredictors of UTIUnivariateMultivariateVariableOR95% CIP valueaOR95% CIP valueFemale1.850.94–3.620.0742.150.95–4.860.065Post-KT UT complication4.491.39–14.500.0127.291.84–28.900.005Non-standard AB prophylaxis2.641.13–6.120.0242.801.03–7.590.043Positive urine donor culture1.840.85–4.000.1191.730.73–4.150.216Diabetes1.710.65–4.490.2732.140.69–6.680.190AsB pre-stent removal2.911.47–5.780.0022.471.13–5.370.023Predictors of recurrent UTIUnivariateMultivariateVariableOR95% CIP valueaOR95% CIP valueAge at KT1.051.00–1.110.0471.061.00–1.210.061UTI ESBL+ pathogen2.301.0–4.480.0405.171.22–21.840.025Post-KT UT complication9.901.11–87.10.04012.970.99–169.90.051