DETECTION OF AMPICILLIN RESISTANCE IN ENTEROCOCCUS SPP BY DISK DIFFUSION AND 2 COMMERCIAL AUTOMATED SYSTEMS

A total of 154 Enterococcus faecium and 48 Enterococcus faecalis isola tes, 55% of which were ampicillin-resistant, were used to evaluate two commonly used automated systems, Vitek's GPS-TA card (bioMerieux, USA ) and MicroScan's POS MIC Type 6 panel (Baxter Healthcare, USA), and t he NCCLS disk diffusion method for the detection of ampicillin resista nce. MicroScan panels were read by the Walk/Away system and by visual inspection. The results were as follows: disk diffusion, 100% sensitiv e and specific; Vitek, 100% sensitive and 95% specific; and MicroScan, when read by the Walk/Away; 85% sensitive and 98% specific. When Micr oScan was interpreted by visual inspection, however,sensitivity increa sed to 96%.