Characterization of E. coli and Total Coliform Organisms Isolated from Wisconsin Waters and Reassessment of their Public Health Significance

Introduction: In 1989 the U.S. Environmental Protection Agency promulgated Revised National Primary Drinking Water Regulations pursuant to the federal Safe Drinking Water Act. For Wisconsin, the law drastically increased the number of water systems required to test for microbiological contaminants. The law also introduced the requirement that laboratories not only look for the “total coliforms” group of bacteria, but also the subgroup of fecal coliforms or E. coli. The law assumes a greater public health risk when fecal coliforms or E. coli are found and thus dictates public notification or “boil water orders.” The number of microbiological contamination events detected and the frequency of “boil” orders has increased drastically because of the Act.

Concurrent with this increased visibility of microbiological contamination events has come a growing suspicion that we, as public health officials, may be unnecessarily alarming the public when, in fact, there is no real public health threat. This suspicion is fueled by recent reports documenting a number of situations in wells and distribution systems where coliform organisms were growing and multiplying in biofilms yielding positive tests, but where no fecal contamination had actually occurred. Another factor to consider is that the profile of coliform species found in drinking water is very different from the coliform profile of feces.