To evaluate the accuracy and cost effectiveness of the AutoSCAN-3 (Micro-Scan Systems of America, Sacramento, Calif.) and Sceptor (BBL Microbiology Systems, Cockeysville, Md.) systems for identification of members of the Enterobacteriaceae, we performed parallel tests on 678 stock cultures of well-characterized clinical isolates of Enterobacteriaceae. Automated results by AutoSCAN-3 correctly identified 95.1% at the genus level and 94.9% at the species level. However, 15 of 42 Shigella isolates were misidentified as members of other genera. In contrast to the automated results, visual interpretation of panels produced 97.9% agreement at the genus level, missing only three Shigella isolates. Sceptor correctly identified 96.8% at the genus level and 93.4% at the species level. Of 42 Shigella isolates, 3 were missed and were designated as Salmonella spp. Although all Salmonella spp. were correctly identified, six other isolates were misidentified as Salmonella spp. Test costs were found to be comparable for each system, with the cost per test increasing markedly with fewer than 10 to 15 tests performed per day.
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