RAPID DETECTION OF SEWAGE CONTAMINATION IN MARINE WATERS USING A FLUOROMETRIC ASSAY OF BETA-D-GALACTOSIDASE ACTIVITY

A simple, rapid method for the detection of faecal coliform bacteria in marine waters is described. The method involves the detection of beta-D-galactosidase, an enzyme marker of coliform bacteria. A fluorogenic substrate (methylumbelliferyl-beta-D-galactoside) is added to a buffered seawater sample and incubated at 44.5-degrees-C for 60 min. The amount of fluorescent label liberated by enzymatic hydrolysis is then determined by instrumental fluorescence spectrometry. Initial field trials show that enzyme activity levels correlate well with faecal coliforms concentrations measured by conventional membrane filtration methods. The enzyme activity level corresponding to the European Community guideline limit for bathing waters of 100 faecal coliforms/100 ml was easily detectable. The method is intended for use as an 'early warning' indicator of sewage contamination events in coastal waters.