RAPID DETECTION OF ESCHERICHIA COLIFORM WITH A BULK ACOUSTIC-WAVE SENSOR-BASED ON THE GELATION OF TACHYPLEUS AMEBOCYTE LYSATE

A new sensing method (BAW-TAL technique), which combined the bulk acou stic wave (BAW) technique with the gelation reaction of Tachypleus ame bocyte lysate (TAL), was used for viscosity and density measurement an d applied to the detection of Escherichia coliform (E. call). This met hod depended on the fact that the viscosity and density of the mixture increased, and as a result, the resonance frequency decreased corresp ondingly after TAL was mixed with the heated E. coli solution that con tained endotoxin. Results showed that the frequency shift was linearly related to the logarithm of E. coli concentration in the range of 2.7 x 10(4)-2.7 x 10(8) cells/ml. The correlation coefficient was 0.996. This BAW-TAL method was compared with the standard pour plate counts ( PPC) method. The proposed method was much more rapid and simpler for d etection of E. coli than the traditional methods. (C) 1998 Elsevier Sc ience B.V. All rights reserved.