New Findings on Isolate-Level UTI Resistance

Investigators from a single Romanian clinical center report isolate-level UTI resistance (2019–2024) using urine culture results generated between 2019 and 2024.

The retrospective dataset included 1,470 patients with clinically suspected lower urinary tract infection, with one urine isolate per patient included in the final analysis. In the species distribution, Escherichia coli represented 66.0% of isolates, followed by Klebsiella pneumoniae and Enterococcus faecalis. Among Gram-negative isolates, the authors reported an extended-spectrum beta-lactamase (ESBL) prevalence of 17.3%.

The authors present the work as isolate-level surveillance drawn from routine urine cultures processed at the center, with antimicrobial susceptibility interpreted using EUCAST criteria.

In the overall isolate set, the highest reported resistance proportions were for ciprofloxacin (35.4%) and trimethoprim–sulfamethoxazole (31.7%). In the E. coli subset, susceptibility to fosfomycin was 99.6% and susceptibility to nitrofurantoin was 92.9%. The tables also show pathogen-to-pathogen differences, with organism-specific profiles provided for K. pneumoniae and E. faecalis.

For independent associations, the authors used multivariable generalized estimating equation models with clustering by patient, modeling resistance (R) versus non-resistance (S/I) for several commonly tested antimicrobials. ESBL production was reported as the strongest independent predictor of resistance across models, with example adjusted odds ratios of 9.83 for ciprofloxacin, 3.22 for amoxicillin–clavulanic acid, 2.89 for trimethoprim–sulfamethoxazole, and 1337 for cefotaxime. Pathogen identity also remained independently associated with resistance, with organism-specific effects persisting after adjustment in several models. In a supportive analysis limited to isolates with MIC data, the median ciprofloxacin MIC was higher among ESBL-positive isolates (4.00 mg/L) than ESBL-negative isolates (0.25 mg/L), while meropenem MICs had a median of 0.25 mg/L with an interquartile range of 0.25–0.25 mg/L. Together, the models and MIC summaries depict resistance as patterned by ESBL status and organism factors within the study’s laboratory dataset.