Oral fosfomycin noninferior to intravenous carbapenems for clinical cure in ESBL-producing Enterobacterales UTIsOral fosfomycin shows promise for treating complicated urinary tract infections

Clinical infectious diseases : an official publication of the Infectious Diseases Society of America Published October 10, 2026 Study authors: Seo Jun-Won, Kim Da Young, Yoon Youngmin, Lyu Young Sang, Na Yong Sub, Moon Do Sik, Yun Na Ra, Kim M… PubMed ↗ DOI ↗ Editorial oversight: Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

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Key Takeaway

Consider oral fosfomycin as a noninferior carbapenem-sparing option for stable patients with ESBL-producing Enterobacterales UTIs.

This multicenter, open-label, randomized noninferiority trial enrolled 299 adults hospitalized with complicated urinary tract infections (UTIs) caused by ESBL-producing Enterobacterales. Patients had already improved after 3 to 7 days of intravenous antibiotics before transitioning to the study intervention.

Participants were assigned to receive either oral fosfomycin trometamol (3 g once daily) or continued intravenous carbapenem or beta-lactam/beta-lactamase inhibitor therapy. The primary outcome was clinical cure, defined as the resolution of UTI-related symptoms and signs within 4 days after treatment completion. The study reported a clinical cure rate of 92.8% (152 patients) in the oral fosfomycin group versus 95.2% (147 patients) in the intravenous group, with a risk difference of -2.47% (95% CI -7.84 to 2.89).

Secondary outcomes included microbiological cure rates. Microbiological cure in urine was 98.0% for oral fosfomycin versus 96.6% for intravenous therapy. Microbiological cure in blood was 97.3% for oral fosfomycin versus 97.5% for intravenous therapy. No data regarding adverse events, serious adverse events, or discontinuations were reported. The study was open-label, which may impact the interpretation of results. These findings may support oral fosfomycin as a carbapenem-sparing strategy for patients with complicated UTIs caused by ESBL-producing Enterobacterales.

How this fits prior evidence

How this fits prior evidence: This study addresses a gap in management strategies for infections involving ESBL-producing organisms. While prior coverage noted that E. coli isolates in Iran show 47.2% ESBL production, this trial specifically evaluates a carbapenem-sparing oral alternative for patients already stabilized on intravenous therapy. It does not directly relate to the findings regarding L. clevelandensis, Pseudomonas aeruginosa, or intravesical aminoglycoside instillations.

Managing a complicated urinary tract infection (UTI) often requires patients to stay in the hospital for intravenous (IV) antibiotics. This can be a long and taxing experience for patients dealing with infections caused by resistant bacteria. Researchers looked at whether switching to an oral medication could be just as effective as staying on IV treatment.

In a study of 299 adults in South Korea, patients were treated for infections caused by specific resistant bacteria. One group received oral fosfomycin, while the other continued IV treatment. The results showed that 92.8% of patients taking oral fosfomycin achieved a clinical cure, which is very close to the 95.2% success rate seen in the IV group. Both groups also showed high rates of clearing the infection from their urine and blood.

While the results suggest that oral fosfomycin is a comparable option to IV drugs for these specific infections, the study was open-label, meaning the researchers knew which patients were receiving which treatment. This is an important finding for doctors looking to manage antibiotic use more carefully while keeping patients comfortable.

What this means for you:

Oral fosfomycin showed similar success rates to IV antibiotics for certain complicated urinary tract infections.

Common questions

Is oral fosfomycin as effective as IV antibiotics for these infections?

The study found that oral fosfomycin had a clinical cure rate of 92.8%, while the intravenous group had a rate of 95.2%. These results were very close, suggesting that the oral medication performed similarly to the IV treatment for patients with these specific types of infections.

What kind of infections was this treatment used for?

The study focused on adults hospitalized with complicated urinary tract infections (UTIs). These specific infections were caused by Enterobacterales that produce certain enzymes, making them harder to treat with standard antibiotics.

Did the medicine clear the infection from the blood and urine?

Yes, the study reported high rates of microbiological cure. Specifically, 98.0% of patients taking oral fosfomycin cleared the infection from their urine, and 97.3% cleared it from their blood, which was nearly identical to the results in the IV group.

Study Details

Study typeRct

EvidenceLevel 2

PublishedOct 2026

PMID42313397

View Original Abstract ↓

BACKGROUND: 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. METHODS: 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. RESULTS: Of the 344 screened patients, 299 were randomized (152 oral fosfomycin; 147 intravenous therapy). Clinical cure occurred in 92.8% of the oral fosfomycin group and 95.2% of the intravenous group (risk difference, -2.47%; 95% CI -7.84 to 2.89), confirming noninferiority. Microbiological cure was similarly high in both groups: urine (98.0% vs 96.6%) and blood (97.3% vs 97.5%). Safety profiles and 30-day outcomes were also comparable. CONCLUSIONS: Oral fosfomycin was noninferior to continued intravenous therapy when used as oral transition therapy for complicated UTIs caused by ESBL-producing Enterobacterales. These findings provide evidence to support oral fosfomycin transition as a carbapenem-sparing antibiotic stewardship strategy for patients with complicated UTIs caused by ESBL-producing Enterobacterales. CLINICAL TRIALS REGISTRATION: KCT0007669.

Oral fosfomycin noninferior to intravenous carbapenems for clinical cure in ESBL-producing Enterobacterales UTIsOral fosfomycin shows promise for treating complicated urinary tract infections

How this fits prior evidence

Common questions

Study Details

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Oral fosfomycin noninferior to intravenous carbapenems for clinical cure in ESBL-producing Enterobacterales UTIsOral fosfomycin shows promise for treating complicated urinary tract infections

How this fits prior evidence

Common questions

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