Evaluation of Extended-Spectrum Beta-Lactamase Production and 28-Day Mortality Predictors in Urine Cultures of Hospitalized Elderly Patients

Introduction: This study aimed to evaluate the associated factors for extended-spectrum beta-lactamase (ESBL) production in Enterobacterales isolated from urine cultures of hospitalized elderly patients and to identify independent predictors of ESBL positivity and 28-day mortality. Methods: A retrospective observational study was conducted at Soma State Hospital involving 261 patients aged 65 years and older hospitalized between January 1, 2025 and January 1, 2026. Bacterial identification and antimicrobial susceptibility testing were performed using the VITEK 2 automated system in accordance with EUCAST guidelines. Risk factors for ESBL production and mortality were determined using multivariate logistic regression models. Results: The median age of the cohort was 81 years, and 64.0% (n = 167) of the isolates were ESBL-positive. While Escherichia coli was the most frequently isolated pathogen overall (48.7%), Klebsiella pneumoniae was the most common organism in the ESBL-positive group (53.3%). Multivariate analysis identified urinary catheter use (aOR = 2.044, 95% CI: 1.178–3.548, p = 0.011) and length of stay of ≥7 days (aOR = 1.905, 95% CI: 1.083–3.352, p = 0.025) as independent risk factors for ESBL positivity. Independent predictors of 28-day mortality included age (aOR = 1.082, p < 0.001), urinary catheter use (aOR = 1.941, p = 0.023), and higher C-reactive protein (CRP) levels (aOR = 1.035, p = 0.036). Notably, ESBL positivity was not significantly associated with mortality (p = 0.076). ESBL-positive isolates exhibited significantly higher resistance rates across nearly all tested antibiotic classes, including ciprofloxacin and trimethoprim-sulfamethoxazole. Conclusion: The findings highlight that urinary catheterization and prolonged hospitalization are pivotal drivers of ESBL prevalence in the geriatric population. Furthermore, advanced age, catheter use, and CRP levels independently impact mortality, underscoring the necessity of monitoring invasive device use to mitigate resistance development and improve clinical outcomes.