title: A comparison of bacterial indicators and methods in rural surface waters.
abstract: The United States Environmental Protection Agency (USEPA) recommends the use of Escherichia coli (E. coli) and enterococci as indicators of enteric pathogens in fresh waters; however, fecal coliform analyses will remain important by virtue of the large amount of historic data collected in prior years. In this study, we attempted, in a real-world situation (i.e., a rural inland watershed in the Piedmont of South Carolina) to compare different bacterial indicators and methods to one another. We compared fecal coliforms, enumerated by membrane filtration with E. coli, enumerated by a commercialized enzyme substrate method and observed E. coli/fecal coliform ratios of 1.63 and 1.2 for two separate tests. In the same watershed, we observed an E. coli/fecal coliform ratio of 0.84 when we used the commercialized enzyme substrate method for both enumerations. Given these results, users of such data should exercise care when they make comparisons between historic membrane filtration data and data acquired through the use of the more modern enzymatic methods. Some sampling and side-by-side testing between methods in a specific watershed may be prudent before any conversion factors between old and new datasets are applied.
authors.affiliation: Earth Sciences and Resources Institute at University of South Carolina, 402 Byrnes Building, Columbia, SC 29208, USA. rwkloot@esri.sc.edu
authors.forename: Robin W
authors.initials: RW
authors.lastname: Kloot
authors.forename: Bobby
authors.initials: B
authors.lastname: Radakovich
authors.forename: Xiaoqing
authors.initials: X
authors.lastname: Huang
authors.forename: Daniel Duke
authors.initials: DD
authors.lastname: Brantley
mesh_terms: D015169:Colony Count, Microbial / Q000379:methods / Q000592:standards; D004755:Enterobacteriaceae / Q000302:isolation & purification*; D004784:Environmental Monitoring / Q000379:methods*; D004926:Escherichia coli / Q000302:isolation & purification*; D005243:Feces / Q000382:microbiology; D005374:Filtration; D045483:Rivers / Q000382:microbiology*; D014871:Water Microbiology; D014876:Water Pollution