Population similarity of enterococci and Escherichia coli in surface waters: A predictive tool to trace the sources of fecal contamination

A biochemical fingerprinting method (the PhPlate system) was used to compare similarities between Escherichia coli and enterococci populations from surface water samples with those found in different animal species during the wet and the dry seasons in order to predict the dominant source(s) of fecal contamination in a local creek. A significant increase in the number and diversity of enterococci was observed in the creek during the wet season. Enterococci population from water samples also showed a higher population similarity with animal species than did E. coli. A higher population similarity was found between both indicator bacteria and animal species during the wet season with highest population similarities found in dogs, horses, cows and kangaroos. In contrast, a low population similarity was found for both fecal indicator bacteria from humans with water samples during the wet and the dry seasons, indicating that humans are not a major source of contamination in the studied creek. The results also indicate that the population similarity analysis of enterococci population has an advantage over E. coli in tracing the possible source(s) of contamination in the studied creek and that population similarity analysis as used in this study can be used to predict the source(s) of fecal contamination in surface waters.