β-glucuronidase activity determination as an indirect estimate of Escherichia coli: development of a miniaturized assay and its application to seawater samples

Background: The search of rapid methods for the detection of Escherichia coli in coastal marine waters is a topic of scientific interest to evaluate potential risks to human health related to their low bacteriological quality. The context and purpose of the study: A miniaturized assay for the analytical determination of β−glucuronidase activity in seawater as a selective marker of Escherichia coli was developed by using the chromogenic Indoxyl-β-D-glucuronide (IBDG) substrate. This compound is specifically cleaved by E. coli, releasing an insoluble chromophoric blue-indigo product that precipitates and is measured at 450 nm wavelength by a microplate reader.