[A study on the disc sensitivity test for fosfomycin (author's transl)]

Susceptibilities to fosfomycin of 216 strains of 28 bacterial species were determined by the 2-fold agar dilution method in parallel with the diameter of inhibition zone by the single-disc method, under the experimental condition establish by Kanazawa. The experiments demonstrated significant correlation between MIC by the dilution method and diameter of inhibition zone in each of conventional assay of the over-night (about 16 hours) incubation, delayed assay (about 24 hours incubation), thus confirming applicability of the single-disc assay for fosfomycin. Analysis of the data obtained by using fosfomycin disc containing 200 micrograms revealed the primary regression equation to be: D (diameter, mm) = 42.73-13.85 log MIC (microgram/ml) in conventional assay, D = 56.51-18.18 log (microgram/ml) in delayed assay, respectively. The range of variations in MICs estimated from the diameter of inhibition zone by the disc test was then calculated in comparison with that in MIC determined by the 2-fold agar dilution assays, as reference for the experimental errors which may be involved in the estimation of MIC of fosfomycin by the single-disc assay.