Comparison ofEnterococcusSpecies Diversity in Marine Water and Wastewater Using Enterolert and EPA Method 1600

Abstract

EPA Method 1600 and Enterolert are used interchangeably to measure Enterococcus for fecal contamination of public beaches, but the methods occasionally produce different results. Here we assess whether these differences are attributable to the selectivity for certain species within the Enterococcus group. Both methods were used to obtain 1279 isolates from 17 environmental samples, including influent and effluent of four wastewater treatment plants, ambient marine water from seven different beaches, and freshwater urban runoff from two stream systems. The isolates were identified to species level. Detection of non-Enterococcus species was slightly higher using Enterolert (8.4%) than for EPA Method 1600 (5.1%). E. faecalis and E. faecium, commonly associated with human fecal waste, were predominant in wastewater; however, Enterolert had greater selectivity for E. faecalis, which was also shown using a laboratory-created sample. The same species selectivity was not observed for most beach water and urban runoff samples. These samples had relatively higher proportions of plant associated species, E. casseliflavus (18.5%) and E. mundtii (5.7%), compared to wastewater, suggesting environmental inputs to beaches and runoff. The potential for species selectivity among water testing methods should be considered when assessing the sanitary quality of beaches so that public health warnings are based on indicators representative of fecal sources.

Enteroccoccus in Water, Sediment and Clams in a Tropical Environment,Maracaibo Lake, Venezuela

“…E. faecalis is the most common specie isolated from clinical samples (80-90%), interacts with many other organisms and has effects on the environment. In the other hand, E. casseliflavus has been reported in 20% of beach samples and it is associated with natural source, such as plants [31][32][33]. This is consistent with the results found in this research.…”

Diversity and antimicrobial resistance of Enterococcus from the Upper Oconee Watershed, Georgia

“…The detection of high numbers of E. casseliflavus in this surface water is similar to findings in some studies but differs from most other studies, as either E. faecalis or E. faecium was reported as the dominant species from surface or other environmental waters (Pinto et al ; Moore et al ; Lata et al ; Luczkiewicz et al ; Lanthier et al ; de et al ). This difference in species distribution could be due to a difference in the isolation method as studies have shown that difference in media and incubation temperatures could select for certain Enterococcus species (Jackson et al ; Ferguson et al ). The difference in species distribution could also be the result of the regional difference as Moore et al (2008) detected different Enterococcus species distribution at separate locations based on the structure of the waterbody and the presence of potential contamination sources.…”

Holding-time and method comparisons for the analysis of fecal-indicator bacteria in groundwater

“…Kinzelman et al (2003) reported the inability to culture and verify enterococcus from Enterolert wells was a drawback with the method. In a method comparison study, Ferguson et al (2013) found that the Enterolert method yielded a higher percentage of non-Enterococcus organisms in surface-water samples than the membrane filtration method on mEI agar. Because of the potential for observing falsepositive results and the added time and cost for verifying Enterolert wells, together with the limitation of a 100-mL sample volume, the mEI method may be more advantageous for analyzing groundwater samples for enterococci than the Enterolert method.…”