Evaluation of Vitek GNI+ and Becton Dickinson Microbiology Systems Crystal E/NF identification systems for identification of members of the family Enterobacteriaceae and other gram-negative, glucose-fermenting and non-glucose-fermenting bacilli

Abstract

We evaluated the Vitek GNI؉ and Becton Dickinson Crystal E/NF identification systems for their ability to accurately identify 619 and 626 strains, respectively, of members of the family Enterobacteriaceae and other glucose-fermenting and non-glucose-fermenting gram-negative rods. All strains tested were taken from a stock collection and passed three times on 5% sheep blood agar prior to testing. These strains represented a more rigorous challenge to both systems than one resulting from the testing of consecutive clinical isolates. Testing with both systems was done according to the manufacturers' instructions, and tests were repeated in duplicate when errors occurred. Vitek version 5.01 and Crystal version 3.0 softwares were used for identifications. The identification results from each system were compared with identifications previously determined with reference biochemicals. At the completion of the appropriate incubation period, the GNI؉ and Crystal systems correctly identified 80.1 and 71.1% of the total isolates, respectively. After additional tests suggested by the software programs were completed, 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 systems 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 associated with no particular organism group. One isolate each of Acinetobacter lwoffii and Vibrio alginolyticus would not grow in the Vitek card. 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 that there was no significant difference (P > 0.05) between the results of the GNI؉ card and those of the Crystal E/NF system after additional testing was performed with the group of organisms tested, but the overall accuracy for both systems in this study was below 90%.

Evaluation of the Wider System, a New Computer-Assisted Image-Processing Device for Bacterial Identification and Susceptibility Testing

“…When analyzed with respect to the organisms tested, the highest essential agreements were observed with isolates of the family Enterobacteriaceae (96.6%) and gram-positive organisms (95.6%). As other investigators have noted with other systems (22,23), lower essential agreement was observed with NFGNRs (88.0%). Nevertheless, in contrast to automated instrument systems with short incubation times (14,15), susceptibility testing results could be obtained for all organisms considered to be slowly growing organisms.…”

“…arizonae ATCC 12323 strain. As with other systems, less accuracy (92.0%) than that observed with isolates of the family Enterobacteriaceae was shown when only NFGNRs were taken into account (8,22,24,25,27). In all cases, the API system was used as the "gold standard" for bacterial identification, as it is a well-recognized system for this purpose (25,31).…”

“…A total of 244 fresh bacterial clinical isolates, prospectively and consecutively collected in our hospital during January and February 1999, were studied. They included 138 isolates of the family Enterobacteriaceae, 25 nonfermentative gram-negative rods (NFGNRs), 51 Staphylococcus spp., 2 Micrococcus spp., 22 Enterococcus spp., and 6 ␤-hemolytic streptococcal isolates. Moreover, 100 clinical Enterobacteriaceae isolates with known resistance mechanisms were also included ( Table 1).…”

Comparison of Vitek GNI and GNI+ Cards for Identification of Gram-Negative Bacteria

“…The results of this study are similar to those reported by Colosante et al (3) in their comparison of GNI and GNIϩ cards. In another study which included an evaluation of the GNIϩ card, O'Hara et al reported an accuracy of 87.6% for the GNIϩ cards; however, the authors acknowledged that the isolates included in their study represented a vigorous challenge to the products evaluated (6). The results of our study for the GNI card are very similar to results reported by Robinson et al (8) and Rhoads et al (7) for the GNI card.…”

Classification, Identification, and Clinical Significance ofProteus,Providencia, andMorganella

“…Commercial methods. With the ever-increasing cost of commercial identification methods (73,74), spot testing is both rapid and cost-effective (64) and can be helpful in many instances. If the colonies on a sheep blood agar plate swarm and are oxidase negative and if a spot indole test using para-dimethylaminocinnemaldehyde reagent is negative, the probability of the culture being either P. mirabilis or P. penneri is very high.…”