A Retrospective Study of Extended Spectrum Beta-Lactamases (ESBL) Urinary Tract Infections Treated with Fosfomycin and in vitro Susceptibility of 102 Isolates to Fosfomycin.

The treatment of urinary tract infections (UTI) caused by extended-spectrum beta-lactamases [ESBL] pathogens has become an increasingly difficult problem due to the limited antibiotics available for therapy. Although fosfomycin has been available for over 40 years, it has not been extensively studied or used in the United States despite being well recognized for its efficacy in the treatment of uncomplicated cystitis. In this study, 102 isolates of ESBL were collected from three hospitals in the southwestern United States and studied for susceptibility to fosfomycin (MIC <16 mm) and the clinical outcomes of 24 adult patients from age 18 years to 85 years of age with ESBL urinary tract infection were also evaluated. 95% of the 92 ESBL isolates studied were susceptible to fosfomycin. Klebsiella species was more likely than E. coli to be resistant to fosfomycin therapy. Despite the small number of patients in this study, the results are encouraging.