Evaluation of the AutoMicrobic system for identification and susceptibility testing of gram-negative bacilli

Abstract

The AutoMicrobic system (AMS) (Vitek Systems, Inc., Hazelwood, Mo.) was compared with the API-20E system for the identification of gram-negative bacilli by using 380 stock clinical isolates and 377 immediately encountered fresh clinical isolates. For the stock isolates, with Enterobacteriaceae-Plus Biochemical Cards and automated interpretation, 364 (95.8%) were in agreement to the species level. For the fresh clinical isolates, agreement at the genus and species levels was 89.7 and 85.9%, respectively, when Enterobacteriaceae-Plus Cards were interpreted by the AMS. Manual interpretation of Enterobacteriaceae-Plus Biochemical Cards improved species level agreement to 91.0%. Subsequent retesting of all discrepant isolates with the Gram-Negative Identification Card resulted in significant improvement of results, and for the stock and fresh clinical isolates, species level agreement was 98.7 and 97.3%, respectively. AMS susceptibility testing was evaluated by comparing ampicillin and cephalothin MICs determined in parallel by AMS and a reference broth microdilution test for stock isolates, and by comparison of AMS and standardized disk agar diffusion test results for fresh clinical isolates. For the stock isolates, AMS mean integer MICs approximated microdilution mean integer MICs with AMS, providing excellent MIC replicability. For ampicillin and cephalothin, 50 and 46.8%, respectively, of AMS integer MICs were within + 1 ,ug/ml of the reference values, and 89.3 and 63.1% of AMS integer MICs were within ±2 ,ug/ml of the reference values. For the fresh clinical isolates, AMS and reference results were in disagreement for 4.5% of the antimicrobial agents tested, with 2.3% as a combination of "major" and "very major" errors.

Identification of Hafnia alvei with the MicroScan WalkAway System

“…More accurate and reliable methods with which to rapidly identify these organisms need to be developed. Some studies on the reliability of automated systems have shown good results, but insofar as the H. alvei strains are concerned, only small numbers were evaluated (34,36,37), with the unique exception of Kelly et al (12), who, using 38 Hafnia alvei strains, obtained results similar (92%) to those in our study.…”

Evaluation of the Cobas-Bact system for direct and rapid identification and antimicrobial susceptibility testing of gram-negative rods from positive blood culture broths

“…When a life-threatening infection is suspected, the important problems are the rapid detection of a pathogen, its identification, and susceptibility testing. A few rapid systems, manual or automated ones, have been marketed and evaluated during the last 10 years (6,8,10,16,17,20). However, all of these systems usually need isolated colonies to start with, a condition which requires at least an overnight incubation of the clinical specimen.…”

Critical evaluation of the AutoMicrobic system gram-negative identification card for identification of glucose-nonfermenting gram-negative rods

“…With the introduction of the AMS GNI, the number of NFGNB species or groups of species this system was capable of identifying increased from 7 to 30 (35). Although one investigator (38) has utilized the AMS GNI card to test all isolates whose identification by EBC-Plus differed from the reference technique, our study is the first to compare the AMS GNI card directly with a standard reference method in the identification of a balanced spectrum of NFGNB. We found the accuracy of the card to be high.…”

“…We were particularly interested in evaluating the ability of the new system to identify NFGNB. Five previous groups of investigators (5,6,17,33,38) have reported on the usefulness of the older EBC-Plus card in the identification of this group of organisms. One (38) utilized the GNI card to test isolates whose identification with the EBC-Plus card differed from that obtained by a reference method.…”