Abundance of Enterococcus species, Enterococcus faecalis and Enterococcus faecium, essential indicators of fecal pollution, in river water

Enterococci such as Enterococcus faecalis and E. faecium are considered as the most suitable indicators of fecal pollution in an aquatic environment, and new methods for Enterococcus determination have been developed, namely, membrane filtration (MF) using membrane-Enterococcus indoxyl-beta-D-glucoside agar (mEI) and defined substrate technology (DST) using Enterolert (R). This study used PCR analysis to identify E. faecalis and E. faecium among Enterococcus strains in river water isolated using both mEI plates and Enterolert (R) trays. There was a significantly high correlation between MF and DST in terms of enterococcal counts for river water samples. The combined percentages of E. faecalis and E. faecium with respect to the total number of all strains obtained using mEI plates and Enterolert (R) trays were approximately 30 % and >30 %, respectively. Other than E. faecalis and E. faecium, a large number of Enterococcus species were unspecified in the actual urban river samples. A comparison of the predominance of E. faecalis and E. faecium found that the abundance of a species depended on the sampling river and date. E. faecium is a non-predominant species in intestinal and fecal Enterococci, and it was one of the main Enterococcus species detected in surface water.