Identification of Enterococcus Species Using a Microplate

Uh, Young; Hwang, Gyu Yul; Jang, In Ho; Yoon, Kap Jun; Lee, Kyungwon; Lee, Hyung Hoan

Abstract

BACKGROUND: The aim of the study was to develop an accurate, convenient, and easy microplate system for the identification of enterococcal species from clinical specimens.
METHODS
The microplate identification method was composed of twelve biochemical tests and identification programs. The tests comprised in microplate were initially screened by a two-tube method, NaCl-esculin hydrolysis and pyrrolidonyl-beta-naphthylamide test; arginine dihydrolase, acid production from mannitol, sorbitol, sucrose, arabinose, raffinose, methyl-alpha-D-glucopyranoside, and ribose in the microplate; and pigment production and hemolytic pattern in blood agar plate. The performance of the microplate for identifying enterococci to the species level was evaluated in comparison with conventional reference tests and commercial kits.
RESULTS
Among the 111 clinical isolates of Enterococcus species, the microplate system correctly identified 100% to genus level, and 91.0% to species level. All of E. casseliflavus, E. durans, and E. hirae were correctly identified by the microplate. The diagnostic sensitivity and specificity for identification of Enterococcus species were as follows: 100% and 96.7% in E. faecium, 93.5% and 100% in E. faecalis, 100% and 97.2% in E. raffinosus, and 33.3% and 98.1% in both E. avium and E. gallinarum.
CONCLUSIONS
It is concluded that the microplate method offers a simple, cost-effective, rapid, and accurate identification system for the identification of most clinical isolates of Enterococcus species.