Direct comparison of two mechanized systems for identification of gram-negative bacilli. Autobac ID system versus the...

The Auto Microbic System (AMS) is an almost completely automated system, capable of identifying Enterobacteriaceae after 8 hours, and some glucose nonfermenters after 13 hours of incubation. The Autobac ID system is a mechanized, computer-assisted system capable of identifying Enterobacteriaceae and many nonfermentative gram-negative bacilli within 3-6 hours. The present report combines the results of two independent studies, both of which evaluated the AMS and the Autobac ID system compared with standard reference tests. Among the 1,510 isolates that were tested, both systems reported equivocal identifications (low confidence values) with 5-6% of the strains. AMS produced fewer erroneous identifications (3.8% vs. 4.9%) but more equivocal test results (5.7% vs. 4.9%). Reproducibility of the two systems was compared by triplicate testing of 88 selected strains in both laboratories. AMS was somewhat more reproducible than the Autobac ID system. The AMS was capable of identifying more species with greater accuracy and reproducibility, but the Autobac ID system was more rapid. Both systems demonstrated excellent accuracy and reproducibility and both could be used efficiently in the clinical laboratory.