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About 97% of Escherichia coli strains produce beta-glucuronidase, but almost all other Enterobacteriaceae lack this enzyme. A D-glucopyranosiduronic acid (glucuronide) possessing a readily detectable beta-linked aglycone should, therefore, constitute a specific reagent for the detection of this organism. For this purpose, the title compound has been synthesized for the first time. The synthesis proceeds in eight steps from readily available D-glucuronolactone, anthranilic acid, and chloroacetic acid and can be carried out on a large scale. The compound has the predicted properties: when included in the standard membrane filter test for the analysis of water, indoxyl-beta-D-glucuronide allows specific detection of E. coli through the formation of blue colonies that are the result of rapid conversion of the liberated aglycone to indigo. The recovery of E. coli is easily measured and almost quantitative.

A new compound, indoxyl-p-D-glucuronide, was assessed as a substrate for the rapid detection ofEscherichia coli in urine. Incorporation of this compound into MacConkey agar allowed the direct differentiation of E. coli as deep blue colonies distinct from lactose and nonlactose fermenters. The sensitivity was 88 to 90%, and the specificity was 100%.

A new medium, mX-Gal, has been developed for the membrane filter enumeration of beta-galactosidase-positive bacteria in municipal water supplies. mX-Gal medium contains the chromogenic beta-galactosidase substrate 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal). All Aeromonas, Citrobacter, and Enterobacter strains isolated from raw water on mX-Gal medium were beta-galactosidase positive. In contrast, only 10 to 20% of these strains produced a red colony with a metallic sheen on m-Endo agar LES medium. Of 674 chlorinated water samples analyzed for total coliforms on m-Endo agar LES medium and for beta-galactosidase-positive bacteria on mX-Gal medium, 18 that were negative for coliforms on m-Endo agar LES showed beta-galactosidase-positive bacteria on mX-Gal. Of a total of 50 beta-galactosidase-positive bacteria isolated from these samples, 76% were identified as Aeromonas hydrophila.

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