Abstract
This investigation was an endeavour to determine whether the presence of viable and culturable cells of the bacterium Escherichia coli, as determined by beta-D-glucuronidase production, can be used as a suitable indicator of the wholesome quality of potable water, as required by current legislation. The presence of Escherichia coli may be taken to indicate faecal contamination, with its associated health hazards, although its absence does not indicate the absence of other potentially pathogenic organisms such as viruses or protozoa, which persist longer in environmental waters. During this study, a variety of different strains of Escherichia coli, both of environmental and clinical origin, were tested repeatedly on different substrates to determine both reliability and reproducibility of beta-D-glucuronidase activity as a measure of contamination. It was found that testing for E. coli by the hydrolysis of 4-methylumbelliferyl beta-D-glucuronide (MUG) incorporated into bacteriological media was reliable in approximately 90% of cases. The presence of glucuronidase was easily demonstrated due to the appearance of the fluorescent hydrolysis product 4-methylumbelliferone in media containing MUG at a concentration of 50 mg per litre. The appearance of fluorescence was faster with this substrate than the other chromogenic media studied. Lactose delayed this reaction, and coloured indicators masked the fluorescence.