Chemiluminescence detection of Escherichia coli in fresh produce obtained from different sources.

A chemiluminescence-based assay is developed for the rapid detection of Escherichia coli in fresh produce. The assay was based on the reaction of beta-galactosidase enzyme from E. coli with a phenylgalactosidase-substituted dioxetane substrate. Light emitted from the reaction was measured in a luminometer and data correlated with counts of E. coli enumerated on sorbitol-MacConkey agar plates. A strain of E. coli O157:H7 was used to inoculate samples of fresh produce to differentiate the inoculum from the natural E. coli potentially present on the produce. Fresh market samples were tested for generic E. coli and E. coli O157:H7. Significant differences in light emission were found in samples with high initial E. coli counts when market samples were compared to respective heat-treated samples. The assay was able to detect E. coli in all produce tested, particularly at higher contamination or inoculation levels. The sensitivity of the assay ranged between 10(2)-10(5) CFU within 30 min. The chemiluminescence assay provides a simple and rapid method for detection of viable E. coli, an important step towards enhancing food safety. Copyright 2004 John Wiley & Sons, Ltd.