INTERPRETIVE CRITERIA FOR CI-960 (AM-1091, PD127391) DISK DIFFUSION TESTS USING 5-MU-G DISKS

CI-960, a new potent fluoroquinolone, was evaluated to develop disk diffusion susceptibility criteria for a 5-mu-g content disk. Preliminary interpretive zone diameter criteria were proposed for two possible susceptible breakpoint MICs (less-than-or-equal-to 1 and less-than-or-equal-to 2-mu-g/ml). Both sets of interpretive criteria performed well having 96.8%-98.4% absolute agreement and no false-susceptible errors. The more conservative less-than-or-equal-to 1-mu-g/ml breakpoint criteria had correlate zones of greater-than-or-equal-to 23 mm for susceptible and less-than-or-equal-to 19 mm for resistant. These criteria produced no false resistance, whereas 0.7% of strains exhibited major errors at the less-than-or-equal-to 2-mu-g/ml breakpoint.