Evaluation of the Vitek GPS-TA card for laboratory detection of high-level gentamicin and streptomycin resistance in

microdilution and disk diffusion methods using high-content disks for the detection of high-level resistance to gentamicin and streptomycin in 99 isolates of enterococci (81 Enterococcusfaecalis isolates and 18 Enterococcus faecium isolates). The GPS-TA card accurately detected high-level resistance to gentamicin, but not streptomycin, in E. faecalis. When streptomycin is being considered for therapy, either disk diffusion or time-kill studies should be used to confirm susceptible results obtained by Vitek testing. Additional studies are needed to determine the best method for testing E. faecium isolates. Bactericidal therapy is recommended for serious entero-coccal infections such as septicemia and endocarditis (3). Synergistic bactericidal activity against enterococci can be achieved by combining a cell wall-active agent, such as penicillin, ampicillin, or vancomycin, with an aminoglyco-side or aminocyclitol. However, enterococci exhibiting high-level resistance (MIC of>2,000,ug/ml) to the aminoglyco-side or aminocyclitol show lack of synergistic killing (3-5, 9, 12). Because high-level resistance in enterococci is increas