Comparison of the Temporal Variability of Enterococcal Clusters in Impacted Streams Using a Multiplex Polymerase Chain Reaction Procedure
Fisher, Jared A.
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Understanding how fecal indicator bacteria and/or fecal indicator genotypes vary over time is important to determine the sources of fecal contamination. Enterococcus is one of the two indicators recommended by the EPA to monitor freshwaters for fecal contamination. Along with Escherichia coli, it has been used by a number of researchers to infer sources of fecal contamination, an area identified as microbial source tracking (MST). Our objective in this study was to identify changes in the seasonal distribution of enterococcal populations in streams directly impacted by cattle farming. The sites under study are located in Madison County, Ga., in farms where cows have unrestricted access to first order streams. Enterococci were counted and isolated monthly from water samples using membrane filtration. The isolates were identified using a multiplex PCR procedure. From a total of nine species identified in stream samples, only the most frequently observed species (E. faecalis, E. casseliflavus, E. flavescens, E. faecium and E. hirae) were used to develop groupings of enterococcal populations via cluster analysis. This analysis revealed that E. casseliflavus and E. faecalis dominated the enterococcal community during spring and fall, respectively. The cluster dominated by E. faecium seemed to increase during winter. This study indicates that enterococcal communities exhibit seasonal variability; and suggests that cluster analysis is a robust approach to identify this variability. In conclusion, to determine the true impact of certain farming operations on stream water quality using enterococcal species as indicators, it is important to consider the temporal variability of key enterococcal communities.