EVALUATION OF VITEK GNI-DICKINSON MICROBIOLOGY SYSTEMS CRYSTAL E( ANDBECTON)NF IDENTIFICATION SYSTEMS FOR IDENTIFICATION OF MEMBERS OF THEFAMILY ENTEROBACTERIACEAE AND OTHER GRAM-NEGATIVE, GLUCOSE-FERMENTINGAND NON-GLUCOSE-FERMENTING BACILLI/

We evaluated the Vitek GNI+ and Becton Dickinson Crystal E/NF identifi cation systems for their ability to accurately identify 619 and 626 st rains, respectively, of members of the family Enterobacteriaceae and o ther glucose-fermenting and non-glucose-fermenting gram-negative rods, All strains tested were taken from a stock collection and passed thre e times on 5% sheep blood agar prior to testing, These strains represe nted a more rigorous challenge to both systems than one resulting from the testing of consecutive clinical isolates. Testing with both syste ms was done according to the manufacturers' instructions, and tests we re repeated in duplicate when errors occurred, Vitek version 5.01 and Crystal version 3.0 softwares were used for identifications, The ident ification results from each system were compared with identifications previously determined with reference biochemicals. At the completion o f the appropriate incubation period, the GNI+ and Crystal systems corr ectly identified 80.1 and 71.1% of the total isolates, respectively. A fter additional tests suggested by the software programs were complete d, the GNI+ had an accuracy of 87.6% and the Crystal system's accuracy had improved to 87.9%, The error rates for the GNI+ and Crystal syste ms were 6.5 and 5.3%, respectively, A report of ''no identification'' was given for 6.0 and 6.9% of the isolates, respectively, and was asso ciated with no particular organism group. One isolate each of Acinetob acter lwoffii and Vibrio alginolyticus would not grow in the Vitek car d, The average times to detection for correct enteric identifications in the GNI+ system were 4.1 and 6.8 h for nonenteric identifications, while the Crystal results were routinely read at 18 h, We conclude tha t there was no significant difference (P > 0.05) between the results o f the GNI+ card and those of the Crystal E/NF system after additional testing was performed with the group of organisms tested, but the over all accuracy for both systems in this study was below 90%.