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

## TL;DR

This 20-year study in Japan shows changing antibiotic resistance in urinary tract infection-causing bacteria, highlighting the need for local data to guide treatment.

## Contribution

The study provides a detailed, long-term analysis of antimicrobial resistance trends in uropathogens at a single hospital.

## Key findings

- ESBL production in Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis increased significantly over 20 years.
- Fluoroquinolone resistance in E. coli and MSSA rose, while it decreased in Enterococcus faecalis and Pseudomonas aeruginosa.
- Resistance rates in E. coli have recently plateaued, but remain high, emphasizing the need for local surveillance.

## Abstract

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.