A Comparison of the Colitag™ Method and the Standard Methods for the Detection of Fecal Coliforms and Escherichia coli in Urban Creeks
Abstract:Fecal contamination in urban wet weather runoff is a major water quality issue. The traditional indicator for fecal contamination has been the coliform count. Recently, methods have been introduced for Escherichia coli(E. coli), a more specific indicator of fecal contamination. One such method is Colitag™ which detects both MUG-positive and MUG-negative E. coli in a single 24 hour test. Unlike other E. coli detecting methods, Colitag™ is not subject to interference from Aeromonas, a ubiquitous aquatic bacterium. We designed a research project to evaluate the convenience and equivalence of the Colitag™ method in a small multi-purpose laboratory. Our reference was the Standard Methods fecal coliform test, the technique currently approved by the U.S. Environmental Protection Agency. From September 2000 to March 2001, 9 wet weather samples and 13 dry weather samples were taken in duplicate from urban creeks in Berkeley, California. The water samples were analyzed by the Colitag™ method in our lab and by the Standard Methods in a certified commercial laboratory. The Colitag™ method was found to be as sensitive as the Standard Methods for detecting fecal coliforms; statistical analysis of parallel test results showed a strong linear correlation of 0.87 between the two methods, a relationship that held up well at both high and low fecal coliform counts. In addition, the Colitag™ method gave rapid and specific enumeration of E. coli and takes only 24 hours compared to up to 96 hours for the Standard Methods. Saving three days means that monitoring agencies could respond faster to sudden increases in E. coli and could therefore take immediate corrective action to ensure public safety.
Document Type: Research Article
Publication date: January 1, 2002
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