Detection of β-glucuronidase in lactose-fermenting members of the family Enterobacteriaceae and its presence in bacterial urine cultures

Abstract

Four hundred strains of lactose-fermenting Enterobacteriaceae were tested for hydrolysis of p-nitrophenyl-β-D-glucopyranosiduronic acid, the chromogenic enzyme substrate of β-glucuronidase. Escherichia coli was found to be homogeneous with respect to β-glucuronidase: more than 94% of the examined E. coli strains were positive, whereas none of the other lactose-fermenting strains possessed β-glucuronidase activity. The qualitative β-glucuronidase test, as rapid and simple as the o-nitrophenyl-β-D-galactopyranosidase test, proved to be of diagnostic value, especially in the identification of E. coli in primary urine cultures. No significant differences were observed in the results of experiments in which either substrate-impregnated disks prepared in the laboratory or commercially available tablets were used.