[Evaluation of an automated system in bacteriology. Application to bacteriological susceptibility tests]

Susceptibility tests have been compared between a new automated system and the reference method by agar diffusion. The COBAS-Micro apparatus for bacterial susceptibility tests is intended for rapid determinations with, normally, an incubation time of 5 h at 37 degrees C. Its is compatible with strains requiring greater than 18 h incubation. With this technique a large range of antibacterial substances (greater than 60) can be studied, in groups of fifteen. With the help of a computerized soft-ware, one growth-index:EPR (End Point Ratio) is calculated, in comparison with a standard, for each antibacterial agent tested and expressed in three categories: SIR. The findings are optimized according to the limits prescribed by the NCCLS. The reference method, by agar-diffusion, is as described by the Comité de l'Antibiogramme de la Société Française de Microbiologie (CA-SFM). A total of 1,048 strains were tested by the two techniques: 518 Gram negative rods, 530 Gram positive cocci, with four common antibiotics. The percentages of agreement between the two groups were: 96% full agreement and minor discrepancy, 4% major and very major discrepancy. This automated system seems to be perfectly suitable for susceptibility testing in a routine laboratory, especially with strains isolated from ambulatory patients.