2261. Oral Fosfomycin for Treatment of Urinary Tract Infections Due to Extended-Spectrum β-Lactamase and Carbapenem-Resistant Enterobacteriaceae

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BackgroundUrinary tract infections (UTIs) caused by extended spectrum β-lactamase (ESBL) and carbapenem-resistant Enterobacteriaceae (CRE) pose a significant challenge due to limited treatment options. The objective of this study was to compare outcomes in patients treated with standard IV therapy or oral fosfomycin for ESBL and CRE UTIs.MethodsRetrospective cohort review of inpatients diagnosed with ESBL and CRE UTIs between June 2016 and September 2017 at a seven-hospital system. Patients with polymicrobial UTI, bloodstream infections, additional anatomical site with ESBL/CRE, or those requiring renal replacement therapy were excluded. Only patients with documented fosfomycin susceptible isolates in vitro were included. Eligible patients were divided into two groups: standard IV therapy (SDTx) or fosfomycin therapy (FOS). FOS group could receive ≤72 hours of other active antibiotics from urine culture collection (UTI onset) to the first dose of fosfomycin. Quick sequential organ failure assessment (qSOFA) scores were calculated at UTI onset. The primary endpoint was functional cure defined as resolution of symptoms without microbiological failure. Microbiological failure was defined as a positive urine culture within the index hospitalization or 30 days.ResultsThere were 70 patients included: 31 treated with SDTx and 39 with FOS. ESBL Echerichia coli was most common, accounting for 58% of UTIs in SDTx and 71.8% in FOS. ESBLs accounted for 71% (n = 22/31) of UTIs in SDTx and 89.7% (n = 35/39) in FOS. The overall qSOFA score was 0.7 (range, 0–3) with the majority of patients scoring < 2 (80.6% in SDTx vs. 92.3% in FOS; P = 0.29). There was no significant difference in functional cure rate (n = 30, 96.8% SDTx vs. n = 37, 94.9% FOS; P = 0.83). SDTx patients had a longer length of stay (15.3 days vs. 7.3 days with FOS; P = 0.04), duration of active therapy (7.6 days vs. 3 days with FOS; P < 0.0001), and time from UTI onset to discharge (10.3 days vs. 6.6 days with FOS; P = 0.002). There were no adverse drug events reported.ConclusionOral fosfomycin was a safe and effective alternative to standard IV therapy for ESBL and CRE UTIs in this investigation and demonstrated similar functional cure rates. Additionally, patients treated with fosfomycin had shorter hospitalizations and durations of antibiotic therapy. Disclosures All authors: No reported disclosures.