This study reports temporal changes in the frequency and antimicrobial resistance profiles of the most commonly isolated Gram-negative bacilli (GNB) from urine cultures processed in a single regional laboratory between 2021 and 2025. A total of 81,791 urine cultures were analyzed to describe evolving susceptibility patterns among uropathogens that commonly drive empirical therapy decisions for urinary tract infections (UTIs).
The authors characterize the overall evolution of resistance in the local area as complex and dynamic and emphasize an upward trend in resistance to several commonly used agents, with implications for empirical treatment and infection control.
The investigation used a cross-sectional, descriptive, retrospective design covering urine cultures from patients with suspected UTIs across the 2021–2025 period. Microbial identification employed either MALDI Biotyper or MicroScan systems. Antimicrobial susceptibility testing was performed using the MicroScan platform and interpreted according to EUCAST guidelines, as reported in the source abstract.
No further demographic breakdowns, specific inclusion criteria for cultures, or denominators by organism beyond the total culture count were reported in the abstract.
Escherichia coli isolates exhibited statistically significant increases in resistance to multiple antibiotics during the 2021–2025 timeframe. Reported agents with rising resistance included amoxicillin-clavulanate, ciprofloxacin, piperacillin-tazobactam and fosfomycin. The most notable change in the abstract was resistance to fosfomycin, which increased from 3.48% in 2021 to 25.31% in 2025. These trends indicate a substantial reduction in susceptibility to agents often used for community and outpatient UTI therapy.
Klebsiella pneumoniae isolates demonstrated marked increases in resistance to several agents. The abstract highlights a particularly large rise in fosfomycin resistance, from 27.25% to 79.73% over the study period. An increase in resistance to imipenem was also reported, suggesting growing carbapenem nonsusceptibility within this species in the study region.
Pseudomonas aeruginosa isolates, which the authors note were predominantly hospital-acquired, showed significant increases in resistance to piperacillin-tazobactam, imipenem, and antipseudomonal cephalosporins. These shifts reflect worsening activity of major anti-pseudomonal agents and raise concerns for management of nosocomial UTIs and more severe urinary tract infections caused by this organism.
The authors call attention to the spread of carbapenemases in uropathogenic GNB as a critical driver of the observed resistance trends. Given the documented increases in imipenem resistance and the high-level rises in resistance to other agents, the study emphasizes the importance of rigorous local epidemiological surveillance and strengthened antimicrobial stewardship programs.
Specifically, the reported results support the need to:
The abstract provides key methodological details but does not report granular demographic data, patient-level clinical outcomes, or detailed sampling criteria in the summary. Any additional limitations or subgroup analyses present in the full text were not described in the abstract. Where the abstract omits further methodological or result details, those specifics are not reported here because they were not available in the source summary.
Between 2021 and 2025 in the reported region, uropathogenic Gram-negative bacilli—notably Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa—demonstrated significant and concerning increases in antimicrobial resistance to commonly used agents, including fosfomycin and carbapenems. The findings underscore the need for continuous local surveillance and active antimicrobial stewardship to inform empirical treatment and infection control policies. The full article (APMIS 2026 Sep;134(9):e70257) should be consulted for detailed methods, organism-specific denominators, and any additional analyses not captured in the abstract.