Results given by Rapid-ATB, a new automated system for the four hour susceptibility testing of bacteria were compared in this study to results given by agar dilution test and disc agar diffusion test. For 100 Enterobacteriaceae strains tested against ten antibiotics, overall agreement between agar dilution test and Rapid-ATB was 99.4%. 6 major discordances concerning especially chloramphenicol were only detected in 1 000 realized susceptibility tests. Overall agreement between agar dilution test and disc agar diffusion test was 96.7%. Eighteen major discordances concerning alike chloramphenicol, but also doxycycline and nalidixic acid, and fifteen minor discordances were detected in this comparison. These results prove the high reliability of this new system which give results more precise than these of disc agar diffusion test.
