Evaluation of the Vitek 2 ID-GNB assay for identification of members of the family Enterobacteriaceae and other nonenteric gram-negative bacilli and comparison with the Vitek GNI+ card.
We evaluated the Vitek 2 ID-GNB identification card (bioMérieux, Inc., Durham, N.C.) for its ability to identify members of the family Enterobacteriaceae and other gram-negative bacilli that are isolated in clinical microbiology laboratories. Using 482 enteric stock cultures and 103 strains of oxidase-positive, gram-negative glucose-fermenting and nonfermenting bacilli that were maintained at -70 degrees C and passaged three times before use, we inoculated cards according to the manufacturer's directions and processed them in a Vitek 2 instrument using version VT2-R02.03 software. All panel identifications were compared to reference identifications previously confirmed by conventional tube biochemical assays. At the end of the initial 3-h incubation period, the Vitek 2 instrument demonstrated an accuracy of 93.0% for the identification of enteric strains; 414 (85.9%) were correctly identified at probability levels ranging from excellent to good, and an additional 34 (7.1%) strains were correctly identified but at a low level of discrimination. Nineteen (3.9%) strains were unidentified, and 15 (3.1%) were misidentified. The 19 unidentified strains were scattered among 10 genera. Three of the 15 misidentified strains were lactose-positive Salmonella spp. and were identified as Escherichia coli; another was a lactose-positive, malonate-negative Salmonella enterica subsp. arizonae strain that was identified as E. coli. Of the 103 glucose-fermenting and nonfermenting nonenteric strains, 88 (85.4%) were correctly identified at probability levels ranging from excellent to good, and 10 (9.7%) were correctly identified, but at a low level of discrimination, for a total of 95.1% accuracy with this group. Two strains were unidentified and three were misidentified. The errors occurred for strains in three different genera. With the increased hands-off approach of the Vitek 2 instrument and accuracies of 93% for the identification of enteric organisms and 95.1% for the identification of nonenteric organisms with the ID-GNB card, use of this product presents an acceptable method for the identification of most gram-negative organisms commonly isolated in the clinical laboratory. A comparison of these results to those obtained by testing 454 of the same strains with the Vitek GNI+ card revealed no significant difference in the abilities of the two cards to identify these organisms accurately.
Epidemiology and Laboratory Branch, Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia 30333, USA. cmo1@cdc.gov
Caroline M
CM
O'Hara
J Michael
JM
Miller
D015373:Bacterial Typing Techniques / Q000295:instrumentation* / Q000706:statistics & numerical data; D004755:Enterobacteriaceae / Q000145:classification* / Q000302:isolation & purification / Q000378:metabolism; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D006090:Gram-Negative Bacteria / Q000145:classification* / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D010088:Oxidoreductases / Q000378:metabolism; D013045:Species Specificity
D010088:Oxidoreductases; D005947:Glucose