INTERPRETIVE CRITERIA FOR DU-6859A DISK DIFFUSION TESTS USING 5-MU-G DISKS

In vitro disk diffusion test interpretive criteria were developed for DU-6859a, a new difluorinated quinolone, using a 5-mu g disk. Included in the 494 organisms tested were 84 (17%) ciprofloxacin-resistant (greater than or equal to 4 mu g/ml) clinical isolates. The following interpretive criteria were proposed for two possible susceptible breakpoint minimum inhibitory concentrations: greater than or equal to 16 mm (less than or equal to 2 mu g/ml) = susceptible and less than or equal to 12 mm (greater than or equal to 8 mu g/ml) = resistant and; greater than or equal to 19 mm (less than or equal to 1 mu g/ml) = susceptible and less than or equal to 15 mm (greater than or equal to 4 mu g/ml) = resistant. These criteria demonstrated greater than or equal to 97% absolute interpretive agreement between test methods with no major (false resistant) or very major (false susceptible) errors.