An assay for the enumeration of total coliforms and Escherichia coli in water and wastewater

A novel pad was developed for identifying the end points of the beta-galactosidase and beta-glucuronidase reactions used in determining total coliforms and Escherichia coli, respectively, in environmental samples. This method (ColiPAD(R)) was run in parallel with the standard multiple tube fermentation (MTF) technique on a total of 33 samples from the influent and treated effluent of two wastewater treatment plants and from a eutrophic lake. Differences in the number of positive tubes by the two methods were not significant for wastewater influent and lake samples and were marginally significant for treated effluents. Regression analysis of log-transformed data yielded highly significant linear correlations between total coliforms by ColiPAD and total coliforms by the MTF method and between E. coli by ColiPAD and fecal coliforms by the MTF method.