Comparison of Urinary Isolate Distribution and Antimicrobial Resistance Profiles in Kidney Transplant Recipients and Non-Transplant Nephrology Patients

Background/Objectives: Urinary tract infections (UTIs) are common infectious complications in kidney transplant recipients (KTRs) and non-transplant nephrology patients. However, direct culture-based comparisons of urinary isolate distribution and antimicrobial resistance profiles between KTRs and non-transplant nephrology (NTN) patients remain limited. This study compared urinary isolates recovered from urine cultures with significant growth and their in vitro antimicrobial resistance profiles in hospitalized KTRs and NTN patients. Methods: In this retrospective culture-based study, urine culture results from patients hospitalized in the nephrology and kidney transplantation units between 1 January 2024 and 31 December 2025 were reviewed. Urinary isolate distribution, in vitro antimicrobial resistance profiles, and extended-spectrum β-lactamase (ESBL) production were compared between the two. Results: A total of 397 patients with at least one urine culture showing significant growth were included, comprising 220 KTRs and 177 NTN patients. Enterobacterales were significantly more frequent among KTRs than among NTN patients (77.2% vs. 41.1%, p < 0.001). Escherichia coli was the predominant urinary isolate in both groups. In contrast, Candida spp. (26.8% vs. 3.2%, p < 0.001), Enterococcus spp. (15.8% vs. 7.7%, p < 0.001), and non-fermenting Gram-negative bacteria (9.4% vs. 3.4%, p = 0.001) were more frequently recovered from NTN patients. Among E. coli isolates, resistance to gentamicin (p = 0.006) and ertapenem (p = 0.001) was significantly higher in the NTN group. Likewise, Klebsiella pneumoniae isolates from NTN patients showed significantly higher resistance to third-generation cephalosporins, aminoglycosides, and carbapenems (p < 0.05). ESBL production was also more frequent in NTN patients than in KTRs (55.7% vs. 41.9%, p = 0.013). Conclusions: Hospitalized KTRs and NTN patients exhibited distinct urinary isolate distributions and in vitro antimicrobial resistance profiles. These findings should be interpreted as culture-based epidemiological data rather than as differences in clinically confirmed UTI burden. Stratified local surveillance may help contextualize urinary isolate and susceptibility patterns across hospitalized nephrology populations.