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

Studies with fosfomycin tromethamine disks containing 200 mug of fosfo mycin and 50 mug of glucose-6-phosphate confirmed the following zone d iameter 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 int ermediate (MIC 128 mug/ml) and greater-than-or-equal-to 16 mm for susc eptible (MIC less-than-or-equal-to 64 mug/ml). Additional studies defi ned acceptable MIC and zone diameter ranges for the following quality control strains: Escherichia coli ATCC 25922, MIC 0.5 to 4.0 mug/ml, z one diameter 23 to 29 nun; Staphylococcus aureus ATCC 25923, zone diam eter 26 to 32 mm; Pseudomonas aeruginosa ATCC 27813, MIC 2.0 to 8.0 mu g/ml; and Enterococcus faecalis, ATCC 29212, MIC 16 to 64 mug/ml.