Susceptibility of multiresistant gram-negative bacteria to fosfomycin and performance of different susceptibility testing methods.

Fosfomycin may be a treatment option for multiresistant Gram-negative bacteria. This study compared susceptibility methods using 94 multiresistant clinical isolates. With agar dilution (AD), susceptibilities were 81%, 7%, 96%, and 100% (CLSI) and 0%, 0%, 96%, and 30% (EUCAST), respectively, for Acinetobacter baumannii, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Enterobacter spp. Categorical agreement between Etest and AD for Enterobacteriaceae and A. baumannii was ≥80%. Disk diffusion was adequate only for Enterobacter. CLSI criteria for urine may be adequate for systemic infections.