INTERPRETIVE CRITERIA AND QUALITY-CONTROL PARAMETERS FOR DETERMINING BACTERIAL SUSCEPTIBILITY TO FOSFOMYCIN TROMETHAMINE

Studies with fosfomycin tromethamine disks containing 200 mug of fosfomycin and 50 mug of glucose-6-phosphate confirmed the following zone diameter criteria for the NCCLS method: less-than-or-equal-to 12 mm for resistant (MIC greater-than-or-equal-to 256 mug/ml), 13-15 mm for intermediate (MIC 128 mug/ml) and greater-than-or-equal-to 16 mm for susceptible (MIC less-than-or-equal-to 64 mug/ml). Additional studies defined acceptable MIC and zone diameter ranges for the following quality control strains: Escherichia coli ATCC 25922, MIC 0.5 to 4.0 mug/ml, zone diameter 23 to 29 nun; Staphylococcus aureus ATCC 25923, zone diameter 26 to 32 mm; Pseudomonas aeruginosa ATCC 27813, MIC 2.0 to 8.0 mug/ml; and Enterococcus faecalis, ATCC 29212, MIC 16 to 64 mug/ml.