Antibiotic Resistance in Urinary Pathogens Among Kidney Transplant Recipients: A Persistent Threat.

Background: Urinary tract infections (UTIs) are the most common infections after kidney transplantation and significantly affect patient outcomes. In these immunosuppressed patients, antibiotic resistance is of particular concern due to recurrent infections and limited treatment options. The aim of this study was to evaluate the distribution of microorganisms isolated from urine cultures of kidney transplant patients and to assess their antimicrobial susceptibility patterns. Methods: This retrospective study included all adult kidney transplant recipients with positive urine cultures during 2023-2024. Microorganisms were identified using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS), and antimicrobial susceptibility testing was performed with the Phoenix System according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines. Results: A total of 363 urine samples from 123 patients (85% female) were analyzed. E. coli (49%) and Klebsiella spp. (24%) were the predominant uropathogens. High resistance rates to ciprofloxacin and trimethoprim-sulfamethoxazole (TMP-SMX) were observed in both species, while carbapenem resistance remained low. Elevated resistance to multiple antibiotics was also detected among Pseudomonas aeruginosa and Acinetobacter spp., highlighting the importance of continued microbiological surveillance in this population. Conclusions: Gram-negative bacteria were the predominant pathogens causing UTIs in kidney transplant recipients. The high resistance rates to ciprofloxacin and TMP-SMX emphasize the need for local antimicrobial surveillance and individualized empirical therapy. Systematic and ongoing monitoring of resistance patterns is essential to optimize infection management in this vulnerable patient group.