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 ab ility to differentiate Escherichia coil from other coliform bacteria r ecovered 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-methylumbe lliferyl-beta-D-glucuronide (MUG) and incubated for an additional 4 h at 35 degrees C. Escherichia coil colonies were distinguished by fluor escence 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. coil. An examination of 182 pu re culture environmental E. coil isolates revealed that 167 isolates ( 91.8%) exhibited fluorescence on the nutrient agar plus MUG medium. Su rvivors of E. coli cultures exposed to chlorination were also capable of producing a positive MUG reaction.