INTERPRETIVE CRITERIA FOR DISK DIFFUSION TESTS USING 5-MICROGRAM CEFDINIR DISKS WITH RAPIDLY GROWING CLINICAL ISOLATES

Preliminary interpretive zone diameter criteria were calculated for the 5-mu-g cefdinir disk diffusion test by using two potential MIC breakpoints (less-than-or-equal-to 0.5 and less-than-or-equal-to 1-mu-g/ml). The absolute agreement between tests ranged from 85.9 to 92.4%, and the false-susceptibility errors were principally contributed by the Enterobacter spp. (2.2% error). One proposed criterion was greater-than-or-equal-to 20-mm zone diameter (less-than-or-equal-to 1-mu-g/ml) for susceptibility and less-than-or-equal-to 16-mm zone diameter (> 2-mu-g/ml) for resistance to cefdinir. Clinical laboratory users of the disk diffusion method should be cautioned about the possibility of very major interpretive errors among enterobacter isolates.