Alessandra Palmisano, Marta D'angelo, Federica Brillo, Daniel Salvetti, Alice Parmigiani, Alessio Di Maria, Francesco Saracino, Eleonora Salsi, Micaela Gentile, Giuseppe Daniele Benigno, Ilaria Gandolfini, Enrico Fiaccadori, Paolo Cravedi, Umberto Leone Roberti Maggiore
ABSTRACT Background Multidrug‐resistant (MDR) Gram‐negative UTIs caused by extended‐spectrum β‐lactamases (ESBL) and carbapenem‐resistant Enterobacteriaceae (CRE) are increasingly common in kidney transplant recipients (KTR), yet their clinical consequences relative to other Gram‐negative infections remain unclear. Methods In this single‐center study from a high‐endemic area, we retrospectively evaluated the impact of MDR colonization ( Colonization ), MDR Gram‐negative infection ( MDR Infection ), presumptive MDR infection (i.e., no isolates available; Presump. MDR ), and non‐MDR Gram‐negative infection ( non‐MDR Inf .) on major post‐transplant complications, including CMV and BKPyV viremia, acute rejection, donor‐specific antibodies (DSA), graft function, and overall transplant failure. We used multivariable cause‐specific hazard Cox regression models with time‐varying covariates and random‐coefficient mixed models. Results Among 521 KTRs, distributed across overlapping conditions, 212 (40.7%) had MDR Colonization , 92 (17.7%) MDR Infection , 61 (11.7%) Presump. MDR , 67 (12.9%) non‐MDR Inf ., and 242 (46.4%) had no infection. Compared with No Infection group, only MDR infection was associated with a steeper decline in eGFR slope ( −5.50 −2.91 −0.33 mL/min/1.73 m 2 per year; p = 0.027) and increased incidence of transplant failure (adjusted hazard, aHR, associated with history of MDR Infection = 1.76 4.11 9.61 ; p = 0.001. MDR infection history was also the only condition associated with CMV viremia (aHR = 1.05 1.83 3.18 ; p = 0.034), and with rejection (aHR = 1.03 1.69 2.76 ; p = 0.036), though it was not associated with BKPyV viremia or de novo DSA. Colonization , Presump. Inf ., and non‐MDR Inf . were not independently associated with complications or transplant failure. Conclusion Documented MDR Gram‐negative UTIs, but not colonization or non‐MDR UTI, are independently associated with acute rejection, CMV viremia, and poorer kidney allograft outcomes.