A rapid fluorogenic method for the detection of Escherichia coli by the production of beta-glucuronidase

A medium containing the fluorogenic substrate 4-methylumbelliferyl-beta-D-glucuronide was developed for the isolation and identification of Escherichia coli within 7.5 h and was based on the detection of beta-glucuronidase. Optimum conditions for the rapid development of fluorescent colonies were determined. The optimum temperature was 41.5 degrees C. Development of fluorescence was delayed when carbohydrates were incorporated into the medium. Water samples were used to evaluate the medium by surface plating and membrane filtration. The frequency of false-negative results was 6.1% and false-positives were 3.7% for freshwater samples. The false-positive organisms were identified as Klebsiella spp. and Shigella sonnei. The potential applications of the medium are discussed.