Shifting Antimicrobial Susceptibility Patterns of Uropathogens: A 20-Year Analysis of Urine Cultures

Antimicrobial resistance among uropathogens, particularly extended-spectrum β-lactamase (ESBL) production and fluoroquinolone (FQ) resistance, presents a significant challenge to treating urinary tract infections (UTIs). This study aimed to analyze 20-year trends in antimicrobial susceptibility among key urinary isolates at a single secondary care hospital in Japan.

We retrospectively analyzed 18 873 urine culture isolates collected between January 2004 and December 2023. Bacterial identification and antimicrobial susceptibility testing were performed according to CLSI guidelines. Temporal trends in ESBL production and FQ resistance rates were analyzed using logistic regression.

Significant increases in ESBL production were observed in Escherichia coli (increasing from 1.4% to a peak of 23.6% in 2020-2021, then settling at 20.4%), Klebsiella pneumoniae, and Proteus mirabilis. FQ resistance also increased significantly in E. coli (from 7.8% to 33.1%), methicillin-sensitive Staphylococcus aureus (MSSA), and Group B Streptococcus (GBS). Conversely, FQ resistance significantly decreased in Enterococcus faecalis and Pseudomonas aeruginosa. Although the rates of ESBL-producing and FQ-resistant E. coli increased overall, they have plateaued in recent years.

This two-decade surveillance revealed complex, species-specific antimicrobial resistance patterns. The high rate of FQ resistance in E. coli, despite a recent plateau, underscores the importance of incorporating local susceptibility data to guide empirical antibiotic selection. Continuous, facility-level surveillance is essential for effective antimicrobial stewardship and for optimizing patient treatment in an era of evolving resistance.