Evaluation of β-glucuronidase assay for the detection of Escherichia coli from environmental waters

Abstract

The new United States Drinking Water Regulations state that water systems must analyze for Escherichia coli or fecal coliforms on any routine or repeat sample that is positive for total coliforms. The proposed methods for the detection of E. coli are based on β-glucuronidase activity, using the fluorogenic substrate 4-methylumbelliferyl β-D-glucuronide (MUG). This study was conducted to determine whether β-glucuronidase negative E. coli were present in significant numbers in environmental waters. Two hundred and forty E. coli cultures were isolated from 12 water samples collected from different environmental sources. β-glucuronidase activity was determined using lauryl tryptose broth with MUG, EC broth with MUG, and the Autoanalysis Colilert (AC) procedure. The isolates were also evaluated by the standard EC broth gas fermentation method for fecal coliforms. The results confirm that assaying for the enzyme β-glucuronidase utilizing the MUG substrate is an accurate method for the detection of E. coli in environmental waters. Key words: Escherichia coli, β-glucuronidase, 4-methylumbelliferyl β-D-glucuronide, water.