Carbapenem Resistance and ESBL-Producing Enterobacteriaceae in Patients with Urological Infections from 2012 to 2021 in Three Korean Hospitals

<b>Background:</b> Urinary tract infections (UTIs) remain a leading cause of community- and hospital-onset bacterial infections worldwide. Although many countries have implemented antimicrobial resistance (AMR) surveillance systems, longitudinal multicenter data on key uropathogens in Korea remain limited. <b>Methods:</b> We retrospectively evaluated <i>Escherichia coli</i> and <i>Klebsiella pneumoniae</i> isolates from patients with clinically diagnosed UTIs at three tertiary-care Korean hospitals (2012-2021). Using a harmonized Observational Medical Outcomes Partnership Common Data Model (OMOP CDM), we analyzed antibiotic susceptibility based on Clinical and Laboratory Standards Institute breakpoints. Trends in resistance to key antibiotics (including fluoroquinolones, cephalosporins, and carbapenems) were assessed using the Cochran-Armitage test. <b>Results:</b> From 2012 to 2021, ESBL-producing <i>E. coli</i> and <i>K. pneumoniae</i> increased from 24.1% to 38.2% and 39.2% to 46.4%, respectively. The rates for <i>K. pneumoniae</i> remained stable over the last 6 years, and for <i>E. coli</i>, they remained stable over the last 3 years. Resistance rates for <i>E. coli</i> increased from 44.5% to 60.0% (ciprofloxacin) and from 26.3% to 40.2% (cefotaxime), while carbapenem resistance (ertapenem) remained low, at 0.3% to 1.2%. In contrast, <i>K. pneumoniae</i> exhibited high resistance levels to fluoroquinolones, cephalosporins, and other broad-spectrum antibiotics, with notable increases in resistance to ertapenem, from 3.0% to 18.1%, and imipenem, from 0.4% to 16.8%. This escalation mainly stemmed from the rise in ertapenem (6.6% to 17.0%) and imipenem (0.8% to 14.6%) resistance rates among <i>Klebsiella</i>-ESBL producers. <b>Conclusions:</b> We conclude that in Korea, the proportion of ESBL-producing <i>E. coli</i> and <i>K. pneumoniae</i> increased significantly from 2012 to 2018 and has since remained stable for the last 3 years (<i>E. coli</i>) and 6 years (<i>K. pneumoniae</i>). Although carbapenem resistance in <i>E. coli</i> remains low, <i>K. pneumoniae</i> has experienced a significant rise, primarily attributable to its ESBL-producing strains. These findings underscore the importance of vigilant antimicrobial stewardship and continuous surveillance to guide empirical UTI therapies in Korean clinical practice.