Abstract

The determination of E.coli as a fecal indicator for surface- and drinking water according to NEN 6261 is based on the ability of E.coli to produce indole from tryptophane. E.coli is also able to use the constitutive enzyme beta-glucuronidase to produce the fluorescent methylum-belliferyl from the substrate 4-methylumbelliferyl-beta-D- glucuronide (MUG). This report describes research on the possibility to use the beta-glucuronidase-activity as an identification- characteristic for E.coli. 14% of the isolated E.coli strains was found to be beta-glucuronidase-negative at 44 degr. C. 24% of these strains showed a positive beta-glucuronidase-reaction at 37 degr. C. Two percent of the isolated E.coli strains was indole-negative and four percent of strains other than E.coli gave false positive reactions in this test. There were no false-positive beta-glucuronidase reactions. It is concluded that the indole-reaction gives better results than the beta-glucuronidase-reaction. The interpretation of the beta- glucuronidase- reaction is more difficult and it gives more false- negative results.