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Project: Enterococcus Speciation in Wastewater and Runoff Sources

Background and Objectives

Current methods for assessing beach water quality are based on quantification of a broadly-defined enterococcal group. Thus, in addition to enumerating Enterococcus species associated with human fecal material such as E. faecalis and E. faecium, species of Enterococcus associated with plants, such as E. casseliflavus and E. mundtii, are also measured as fecal indicators. The advent of molecular methods provides the opportunity to measure the individual Enterococcus species that are most closely associated with fecal sources, but it is unclear which species are most appropriate for use in molecular method development. The goal of this study was to compare the species distribution of Enterococcus in the influent and effluent of four wastewater treatment plants with the species distribution in freshwater runoff and beach water to better define the species associated with human waste streams.


This study was conducted from 2005 to 2007.


A total of 1,280 presumptive enterococci isolates were identified to species level using Vitek and biochemical testing.


E. faecium and E. faecalis were the predominant species in wastewater, accounting for more than two-thirds of all isolates. Species compositions for beach samples and freshwater differed significantly from those found in wastewater, with most of the difference attributable to the presence of E. casseliflavus. E. casseliflavus accounted for 22% of the isolates in beach water, but less than 4% in wastewater (Figure 1). This pattern is consistent with previous clinical studies that have established E. faecium and E. faecalis as prevalent in human fecal material, as well as field studies that have identified an affiliation between E. casseliflavus and decaying plant material. These findings suggest an opportunity to provide a narrower definition of Enterococcus for purposes of beach water quality monitoring and health risk assessment.

Figure 1. Enterococcus speciation


Orange County Sanitation District
Orange County Public Health Laboratory
Los Angeles County Sanitation District
South Orange County Wastewater Authority
Encina Wastewater Authority

For more information on Enterococcus Speciation in Wastewater and Runoff Sources, contact John Griffith at (714) 755-3228.
This page was last updated on: 7/2/2014