Rapid enzymatic detection of Escherichia coli contamination in polluted river water

Aims: The relationship between the rate Of beta -D-glucuronidase hydrolysis (GLUase-HR) and the E. coli concentration in rivers differing in the extent of faecal pollution was investigated. It was hypothesized that the rate of GLUase-HR is a better surrogate parameter for E. coli concentrations than estimated numbers of faecal coliforms (FC). Methods and Results: The GLUase-HR of the water sample filter residues was determined as the rate of cleavage of 4-methylumbelliferyl-beta -D-glucuronide. FC and E. coli concentrations were enumerated using mFC and Chromocult Coliform agar, respectively. Regression analysis revealed that a 90% variation of the variable log GLUase-HR was directly related to the variable log E. coli concentrations. The observed relationship between the log of the FC count and the log of the GLUase activity could be explained by the hydrolysis activity of the E. coli population, as E. coli is a part of the FC group. Conclusions: The data suggest that the log of the GLUase-HR can be used as a surrogate parameter for the log of the E. coli concentrations. Significance and Impact of the Study: GLUase-HR determination may provide a rapid alternative technique to estimate E. coli concentrations in freshwaters.