Oral Fosfomycin for Resistant UTIs

Why Did COVID-19 Increase Concern About Antibiotic Resistance?

The CDC's COVID-19 and antimicrobial resistance review describes a setback with lasting implications for treatment. Resistant infections beginning in hospitals, and associated deaths, each increased by at least 15% across seven pathogens between 2019 and 2020. These are historical surveillance findings, not newly measured October 2026 infection rates. The agency also describes shortages, longer admissions and increased use of devices such as ventilators and urinary catheters. [CDC review](https://www.cdc.gov/antimicrobial-resistance/data-research/threats/covid-19.html)

Antibiotics cannot treat the virus that causes COVID-19, although bacterial infections occurring alongside it may require them. The treatment challenge extends beyond avoiding unnecessary prescriptions: clinicians also need effective alternatives when resistant bacteria leave patients dependent on intravenous drugs. Research into oral treatment after initial stabilization addresses that problem, although its effect on population-level resistance requires separate study.

What Did the Oral Fosfomycin Trial Find?

A randomized, open-label trial published in the International Journal of Infectious Diseases enrolled 124 adults with complicated urinary infections caused by Enterobacterales resistant to third-generation cephalosporins. After initial IV therapy, participants switched to oral fosfomycin or continued a carbapenem, completing seven treatment days overall. Clinical cure at day seven reached 98.4% in each group. [Randomized trial](https://pubmed.ncbi.nlm.nih.gov/42217749/)

The findings support a possible alternative to continued carbapenem exposure, but they do not establish oral fosfomycin as a substitute for initial IV treatment. Both groups had already received active intravenous antibiotics. The small sample and open-label design limit certainty, and the study did not demonstrate that switching treatment reduced subsequent antibiotic resistance.

Who Might Be Considered for Oral Fosfomycin After IV Treatment?

IDSA's July 2026 guidance remains cautious: oral fosfomycin is not suggested as initial treatment for complicated urinary infections because concentrations in kidney tissue are limited. It may be considered after IV therapy for selected infections caused by ESBL-producing E. coli when other oral options are unavailable. ESBLs are bacterial enzymes that disable several commonly used antibiotics. [IDSA treatment guidance](https://www.idsociety.org/practice-guideline/amr-guidance/)

Patient selection is crucial. The 124-person trial excluded pregnant patients, those with concurrent bloodstream infection and people whose bacteria resisted the study drugs, according to IDSA's accompanying review. Its findings therefore cannot establish effectiveness in those groups. A switch requires an individualized assessment; persistent illness or a bloodstream infection cannot be treated as equivalent to the population studied. [IDSA trial review](https://www.idsociety.org/science-speaks-blog/2026/treating-cutis-with-oral-fosfomycin-after-carbapenems/)