Oral fosfomycin use for pyelonephritis and complicated urinary tract infections: a 1 year review of outcomes and prescribing habits in a large municipal healthcare system.

ABSTRACT

BACKGROUND: The rising incidence of MDR uropathogens has driven increased use of oral fosfomycin for treatment of complicated urinary tract infections (cUTIs). However, there are limited data to support its use for cUTI, especially pyelonephritis. METHODS: We performed a retrospective review of all oral fosfomycin prescriptions between 1 January and 31 December 2017 in the Los Angeles County Department of Health Service system, the second largest US municipal health system. We examined demographics, clinical characteristics, adverse events and 30 day treatment success for patients with cUTI. Follow-up urine cultures till 31 December 2018 were examined for emergence of fosfomycin resistance. RESULTS: Of 154 patients prescribed fosfomycin, 99 (64%) had cUTI. Of these, 39 (39%) had lower tract, 37 (37%) pyelonephritis and 23 (23%) non-pyelonephritis upper tract cUTI. Escherichia coli ESBL producers were the predominant pathogens (73%). Of the 63 patients with 30 day follow-up, 49 (78%) had clinical success, including 16/20 (80%) treated for pyelonephritis. Treatment failure was associated with male sex (P < 0.01), urological abnormalities (P = 0.05), non-E. coli cUTI (P = 0.03) and receipt of <25% IV therapy prior to fosfomycin switch (P = 0.03). Of patients prescribed fosfomycin (n = 154), fosfomycin-resistant E. coli were found in 9/64 (14%) of the patients with follow-up urine cultures >30 days after initial treatment. CONCLUSIONS: Despite the lack of data supporting its use, we found that most patients receiving oral fosfomycin off-label for cUTI, including pyelonephritis, had clinical success. However, emergence of subsequent resistance warrants caution. Prospective comparative studies should be done to better evaluate oral fosfomycin use for cUTI.