Background：Several automated and nonautomated systems have been developed and are commercially available for the identification of gram-negative bacilli. EASY 24E+ kit was recently developed as Korean kit for identification of gram-negative bacilli. So we evaluated the accuracy and clinical utility of EASY 24E+ compared with API 20E and VITEK GNI+.

Methods：The 221 clinical isolates of Enterobacteriaceae, including 17 C. freundii, 20 E. cloacae, 31 E. coli, 6 E. aerogenes, 29 K. pneumoniae, 3 K. oxytoca, 11 M. morganii, 13 P. mirabilis, 16 Salmonella  spp., 20 S. marcescens, 9 Shigella spp.,22 S. sonnei, 16 S. typhi, 8 Y.  pseudotuberculosis and 10 control strains were identified by API 20E, EASY 24E+, and VITEK GNI+. Discrepant strains were performed repeat identifications and we evaluated overall accuracy.

Results：All of control strains were correctly identified by three systems. The overall correct results at species level and at the genus level for 221 clinical isolates, were 96.8% and 99.1% by the VITEK GNI+, 97.7% and 97.7% by the EASY 24+ and 99.1% and 100% by the API 20E. All of Salmonella spp., S. typhi and Shigella spp. were correctly identified by all three systems and the discrepant identifications of species were 2 Y. pseudotuberculosis, 3  K. pneumoniaeand 2 K. oxytoca by VITEK GNI+, 4 C. freundii and 1 P. mirabilis by EASY 24+, and 2 S. marcescens by API 20E.

Conclusions：All three identification systems are accurate methods for the identification of Enterobacteriaceae, and EASY 24+ is comparable with API 20E and VITEK GNI+. (Korean J Clin Microbiol 2001;4(2):96-101)