Rapid enumeration methods based on the enzymatic hydrolysis of 4-methylumbelliferyl-#beta#-D-galactoside and 4-methylumbelliferyl-#beta#-D-glucuronide were optimized for freshwaters. The enzymes #beta#-D-galactosidase (GALase) and #beta#-D-glucuronidase (GLUase) were shown to be already induced in freshwaters when tested, respectively. with the inducers isopropyl-#beta#-D-thiogalactopyranoside and methyl-#beta#-D-glucuronide. Both enzymatic activities were compared, respectively, with plate counts of total and faecal coliforms in freshwaters. Enzymatic methods and reference plate counts were significantly correlated in log-log plots. Moreover, the GLUase method allowed the detection of viable (presenting a detectable GLUase activity) but nonculturable Escherichia coli.
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