Detection of Escherichia coli by the nutrient agar plus 4-methylumbelliferyl beta-D-glucuronide (MUG) membrane filter method.

A two-step membrane filter procedure was evaluated to determine the ability to differentiate Escherichia coli from other coliform bacteria recovered from water. M-Endo LES agar incubated at 35 degrees C for 24 +/- 2 h was used as the initial isolation medium. Membranes containing coliform colonies were transferred to nutrient agar plus 4-methylumbelliferyl beta-D-glucuronide (MUG) and incubated for an additional 4 h at 35 degrees C. Escherichia coli colonies were distinguished by fluorescence when viewed under a long-wavelength ultraviolet light. A total of 119 MUG-positive colonies were isolated from 15 water sources, of which 115 (96.6%) were identified as E. coli. An examination of 182 pure culture environmental E. coli isolates revealed that 167 isolates (91.8%) exhibited fluorescence on the nutrient agar plus MUG medium. Survivors of E. coli cultures exposed to chlorination were also capable of producing a positive MUG reaction.