Rapid identification of Enterobacteriaceae with microbial enzyme activity profiles

A total of 539 clinical isolates belonging to 10 species of the Enterobacteriaceae family were identified by enzyme activity profiles within 30 min of test inoculation. Each isolate was grown at 37 degrees C for 18 h on Mueller-Hinton agar and suspended to an optical density of 200 Klett units on 0.85% saline. Enzyme activity profiles were obtained by inoculating 18 fluorogenic substrates with the standardized bacterial suspension and monitoring initial rates of hydrolysis over the first 30 min of analysis. Individual enzyme activity profiles were entered into a coded data bank, and identifications were based on the Bayesian theory of probabilities. At a confidence level of 95%, five species were identified with a greater than 90% efficiency, three species were identified between 83 and 88% efficiency, and two species demonstrated a 72 and 75% efficiency of identification. The enzyme activity profile method of bacterial identification is rapid, easily automated, and reproducible.