Fosfomycin as Oral Transition Therapy Versus Continued Intravenous β-Lactams for Complicated Urinary Tract Infections Caused by Extended-Spectrum β-Lactamase-Producing Enterobacterales: A Multicenter, Open-Label, Randomized Controlled Trial

Extended-spectrum β-lactamase (ESBL)-producing Enterobacterales are an increasing cause of complicated urinary tract infections (UTIs). Reliance on carbapenems to treat these infections accelerates resistance, underscoring the urgent need for effective oral transition options to preserve last-line agents and lessen healthcare burden.

We conducted a multicenter, open-label, randomized, noninferiority trial at four tertiary hospitals in South Korea (November 2022-June 2025). Adults hospitalized with complicated UTIs due to ESBL-producing Enterobacterales who improved after 3-7 days of intravenous antibiotics were randomized (1:1) to either continue intravenous carbapenem or β-lactam/β-lactamase inhibitor therapy or switch to oral fosfomycin trometamol (3 g once daily). The primary outcome was clinical cure, defined as resolution of urinary tract infection-related symptoms and signs within 4 days after completion of treatment. Secondary outcomes included microbiological cure, readmission, adverse events, and 30-day recurrence.