[Studies on the disc method for the determination of bacterial sensitivity to ribostamycin (author's transl)].

The MICs of ribostamycin (RSM) were determined by the two-fold serial agar-dilution method of 109 bacterial strains of 20 species. The diameters of inhibition zones of these bacterial strains by the 50 mug RSM disc were also measured. The relation between the MIC and the diameter of the inhibition zone was found to be expressed as a primary regression line in all cases of the conventional method (cultured for about 16 hours), delayed assay method (cultured for about 24 hours) and rapid methods (5 approximately 6 hours and 3 approximately 4 hours culture methods). Thus, it was confirmed that the single-disc method can be employed for the susceptibility test of RSM. Subsequently, variations of MICs obtained by the disc-diffusion method were compared with those obtained by the serial agar-dilution method.