65 - Impact of a Multifaceted Stewardship Intervention on Oral Fosfomycin Prescribing for Treatment of Resistant Organisms in Cystitis

Background: Fosfomycin is an oral antibiotic with activity against multi-drug resistant (MDR) bacteria that is recommended as first line treatment for cystitis. The ability to use an oral agent for these infections will be beneficial due to the decreased need for hospitalizations and clinic visits to manage IV therapy; therefore, reducing healthcare exposure for the patient.

Methods: This was a multi-site, observational study evaluating adult patients with a urine culture growing extended-spectrum beta-lactamase E. coli, vancomycin-resistant Enterococcus, or fluoroquinolone-resistant Pseudomonas urinary isolates and with documented cystitis between September – November 2018 (pre-implementation) and September – November 2019 (post-implementation). The primary outcome was the difference in the rate of fosfomycin use pre and post implementation of multiple stewardship interventions (routine fosfomycin susceptibility reporting on MDR organisms, creation of a fosfomycin order set and provider education).

Results: Of 306 patients reviewed, 148 patients met eligibility criteria (68 pre, 80 post). The majority of patients were female (80%), diagnosed with complicated UTI (82%), treated outpatient (88%), and with ESBL E. coli as the causative pathogen (91%). There was a significantly higher rate of fosfomycin use post-intervention (pre 1.5% vs. post 20%, p< 0.001). No difference was seen between groups in the rates of use of all other antibiotic classes. The most common antibiotic prescribed for empiric or definitive therapy was nitrofurantoin (empiric 43%, definitive 53%). Appropriate fosfomycin dosing was low in both groups (pre 9% vs. post 19%; p > 0.99). There was no difference in the rate of adverse reactions (pre 4% vs. post 5%, p > 0.99).

Conclusion: There was an increase in fosfomycin use after incorporating a multifaceted stewardship intervention. Fosfomycin provides an alternative oral option for MDR urinary isolates and was not shown to be associated with an increase in adverse effects. This was a simple stewardship intervention which made a measurable impact on antimicrobial use. Additional education for providers and pharmacists regarding appropriate dosing could be considered in the future to promote optimal use.