Title: Comparative Outcomes of Oral Beta-Lactams Versus Fluoroquinolones or Trimethoprim-Sulfamethoxazole for Step-Down Therapy in Enterobacterales Bacteremia Secondary to Urinary Tract Infections
Primary: Taylor Hewitt Secondary: Jordyn Meredith, Joseph Crosby, Courtney Zeigler
Background: This single-center, retrospective, observational cohort study was conducted at St. Joseph’s/Candler Health System to assess treatment failure in patients with Enterobacterales bacteremia secondary to urinary tract infections (UTIs) who received oral step-down antibiotic therapy. The study included patients hospitalized between January 1, 2022, and August 1, 2025, identified using ICD-10 codes for bacteremia. Electronic medical records were reviewed to confirm infection from a urinary source, requiring matching positive urine and blood cultures for Escherichia coli, Klebsiella spp., or Proteus spp. Eligible patients were adults (≥18 years) who received parenteral antibiotics during admission, followed by oral step-down therapy with either a beta-lactam, fluoroquinolone (FQ), or trimethoprim-sulfamethoxazole (TMP-SMX). Exclusion criteria included polymicrobial bacteremia, absence of oral step-down therapy, discharge to hospice, or pregnancy. Patients were stratified into two groups: those who received oral beta-lactams versus those who received FQ or TMP-SMX. The primary outcome was treatment failure, defined as a recurrent positive urine or blood culture for the same organism within 60 days of the initial diagnosis. The secondary outcomes included duration of therapy (both parenteral and oral), and hospital length of stay. Descriptive statistics summarize baseline characteristics and outcomes. Continuous variables were analyzed using Student’s t-test, and categorical variables using chi-square tests or appropriate non-parametric alternatives. Analyses were performed using Microsoft Excel, with statistical significance defined as a two-sided p-value < 0.05.
Results: Thirty-eight patients were enrolled in this study, including 11 patients who received oral beta-lactams and 27 patients who received fluoroquinolones (FQ) or trimethoprim-sulfamethoxazole (TMP-SMX). The primary outcome of treatment failure occurred in 7 patients (64%) from the beta-lactam group and 1 patient (4%) from the FQ/TMP-SMX (p=0.00004). No significant difference was found between the two groups for secondary outcomes duration of therapy and hospital length of stay.
Conclusion: In this study assessing treatment failure in patients with Enterobacterales bacteremia secondary to urinary tract infections (UTIs) who received oral step-down antibiotic therapy, a higher percentage of patients experienced treatment failure in the beta-lactam group compared to the FQ/TMP-SMX group. The secondary outcomes of length of hospital stay and duration of therapy were similar across both groups. Potential limitation factors include inability to assess adherence to antibiotic therapy outpatient and step-down to oral therapy occurring at different points within the hospital stay. Future studies should target a larger population with only in-patient stepdown therapy due to the traceability of patients receiving antibiotics.
