Evaluation of Identification Rate of Enterobacteriaceae by Conventional Biochemical Tests

Uh, Young; Hwang, Gyu Yel; Son, Jeong Seog; Jang, In Ho; Yoon, Kap Jun

Abstract

BACKGROUND: One of major consideration of any identification (ID) system is the cost. Commercial kits, however, are too expensive. The aim of this study was to evaluate the clinical usefulness of the computerized ID system based on the conventional minimal biochemical tests for the identification of clinical isolates of Enterobacteriaceae.
METHODS
During June 1996 to April 1997, Enterobacteriaceae were tested by triple sugar iron, motility, indole, ornithine decarboxylase, and citrate, and 2-4 biochemical tests were tested additionally according to the characteristics of colony on MacConkey agar. We also compared the conventional ID system with API Rapid 32E (ATB system, bioMrieux, France) to determine the accuracy of conventional ID system.
RESULTS
Among the 3,652 strains of Enterobacteriaceae, 84.4% were identified by conventional tests. The identification rate of Enterobacteriaceae by conventional tests; K. pneumoniae, E. coli, P. stuartii, M. morganii, and P. mirabilis were more than 80%; K. oxytoca, Enterobacter, and S. marcescens were ranged from 70% to 80%; P. vulgaris, P. rettgeri, and C. freundii were less than 70%. Among the 133 isolates tested simultaneously by two ID systems, each of one strain of M. morganii, E. cloacae, and S. marcescens on conventional minimal biochemical tests were identified as E. coli, E. sakazakii, and S. liquefaciens by commercial kit.
CONCLUSIONS
Our computerized ID system based on the minimal biochemical tests was found to offer simple, reliable and economic in the identification of clinical isolates of Enterobacteriaceae. And further studies are needed for the improvement of accuracy and identification rate.