Comparison of methods for the interpretation of disk diffusion susceptibility tests for augmentin.

Disk diffusion susceptibility tests for Augmentin were performed on 239 patients isolates. They were interpreted by means of Stoke's criteria, the ICS method, and a modified error minimization technique. A reference minimal inhibitory concentration of less than or equal to 16 mg/L was chosen to correspond to likely therapeutic success in urinary tract infection and the performance of each method was compared. Zone radii of inhibition correlated well with the minimal inhibitory concentration. A single urinary breakpoint for susceptibility could be established by means of the error minimization technique (Zs greater than or equal to 6 mm radius) which classified 1% of strains as falsely susceptible. The false-resistant rate, however, was increased to 14% and alternative test conditions are advised if true rates of resistance are to be determined. Use of an indeterminate category (4 less than Z1 less than 6 mm radius) is recommended when the rate of resistance is in excess of 20% but not otherwise.