Please find the link for the following US EPA method

Improved Enumeration Methods for the Recreational Water
Quality Indicators: Enterococci and Escherichia coli

Abstract:
In 1986, the U.S. Environmental Protection Agency (USEPA) recommended two new indicator organisms for recreational water quality assessment. They were enterococci (for both marine and fresh waters) and Escherichia coli (E. coli, for fresh waters only). These organisms were chosen based on epidemiological studies conducted at various beaches in the United States that showed a strong positive correlation between the organisms and the occurrence of swimmingassociated gastroenteritis. The two new target organisms required the use of media designed specifically for enumeration of them from ambient waters. Since then, these two media (mE Agar for enterococci and mTEC Agar for E. coli) have been improved, resulting in faster and easier enumeration. The modified media are mEI Agar for enterococci and modified mTEC Agar for E. coli. The purpose of this manual is to provide specific step-by-step instructions for both the original and the revised test methods (mE, mEI, mTEC, and modified mTEC) used for the new USEPA recommended recreational water quality indicators. This manual is intended to supplement the 1999 USEPA video entitled Improved Enumeration Media for the Recreational Water Quality Indicators Enterococci and Escherichia coli, although it may be used without the video.

http://www.epa.gov/nerlcwww/RecManv.pdf