In this paper, we report on the amplification by polymerase chain reaction (PCR) of a 509 base sequence unique to E. coli O157:H7. Immobilization of a probe for the bacterium on an acoustic wave sensor by the biotinâ neutravidin interaction was employed to detect the on-line hybridization of the sequence with the sample obtained from PCR. The limit of detection was found to be 10^{â 8} M, which suggests that the method may be useful for detecting the organism in food, water and clinical samples. Finally, this approach lays the groundwork for incorporating the method into an integrated system for rapid PCR-based DNA analysis.