Submitted to: Society of Environmental Toxicology and Chemistry Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 5/18/2004
Publication Date: 5/27/2004
Citation: Schaubhut, M., Burns, M., Mikell, A.T., Moore, M.T., Cooper, C.M., McElwain, L., Williams, L. 2004. The characterization of E. coli through U. S. Environmental Protection Agency approved standard methods [abstract]. Mid-South Regional Society of Environmental Toxicology and Chemistry. p. 26. Interpretive Summary:
Technical Abstract: The fecal coliform, Escherichia coli, is a historical organism for the detection of fecal pollution in water supplies. The presence of E. coli indicates a potential contamination of the water supply by other more hazardous human pathogens. In order to accurately determine the presence and degree of fecal contamination, it is important that the standard methods, approved by the U.S. Environmental Protection Agency, designed to determine the presence of E. coli in a water supply distinguish E. coli from other coliform bacteria, such as those of the genera Citrobacter, Klebsiella, and Enterobacter. These genera of bacteria are present in fecal matter but also in soil and water sediment, and thus are not good indicators of fecal contamination. Standard methods must also yield results that agree with each other. In an experiment of local recreational water supplies of north Mississippi, only approximately 45% of bacterial isolates did not show conflicting results in mF-C, in EC, and on EMB agar plates when all tests were allowed to incubate at temperatures approved by the U.S. Environmental Protection Agency for 24 h. There is ambiguity in determining a positive result on mF-C filters by a blue colony. When all variations of blue, light blue or glossy blue, for example, were examined, they produced results that agreed with the mF-C results less often when colonies the technician termed blue with no descriptors were examined. In a similar study, approximately 53% of samples producing a blue colony on mF-C media were found to be E. coli using API-20E test strips. The other genera of bacteria that produced a blue colony on mF-C were identified as Klebsiella in 16% of the samples, Enterobacter in 11% of the samples, and Citrobacter in 3% of the samples when the identity was determined on API-20E test strips.