Susceptibility of Clinical Isolates of Escherichia coli to Fosfomycin as Measured by Four In Vitro Testing Methods

Clinical isolates of Escherichia coli ( n = 554) were tested against fosfomycin using agar dilution, disk diffusion, and Etest. Agar dilution (reference method) identified few isolates with fosfomycin MICs of 64 ( n = 3), 128 ( n = 4), and ≥256 μg/ml ( n = 2). Applying CLSI (M100, 2020) and EUCAST (v. 10.0, 2020) breakpoints, 98.9% and 98.4% (agar dilution), 99.