Direct Comparison of Antimicrobial Susceptibility Testing by the BD Phoenix, bioMérieux ViTek 2, and Disk Diffusion Test Methods as Compared to Results Generated by the CLSi Broth Microdilution Test

BACkGRounD. Several options exist for performance of automated or manual antimicrobial susceptibility testing in clinical laboratories. We have assessed the use of the BD Phoenix, the bioMerieux V iTek 2, and the CLS i disk diffusion methods for testing common, aerobic bacteria. MeThoDS. A collection of fresh clinical isolates and stock strains were tested in common by the three methods. They included staphylococci, enterococci, members of the Enterobacteriaceae, and selected species of non-fermenters. Results were compared to MiCs determined using the CLS i broth microdilution method with specially prepared frozen panels. ReSuLTS. A total of 410 commonly encountered aerobic pathogens (180 fresh clinical isolates, 230 stock strains) were tested. overall susceptibility category agreements between the test methods and the reference procedure were 95.3% for Phoenix, 95.1% for ViTek 2, and 94.7% for disk diffusion. Percent very major (VM) , major (M), and minor (m) error rates were 1.2, 1.8, and 3.2 for Phoenix, 2.7, 0.2, and 3.9 for V iTek 2, and 1.4, 0.2, and 4.5 for disk diffusion using the relevant organism-drug combinations successfully tested by each method. When on-scale MiCs were obtained with the two instruments, the overall essential agreement (+/- one dilution) between the reference method and Phoenix was 91.7% and was 89.1% with ViTek 2. Differences