Improving the Identification of Fecal Contamination in Recreational Water through the Standardization and Normalization of Microbial Source Tracking

Recreational water quality monitoring (RWQM) is essential for reducing the risk of exposure to waterborne pathogens from fecal contamination. Human fecal contamination poses the most significant risk due to the host-specific nature of many pathogens. Traditional RWQM cannot differentiate between human and nonhuman fecal contamination, limiting its application. Microbial source tracking (MST) is a method introduced to improve RWQM by characterizing fecal contamination by source. This method relies on the detection of host-specific DNA targets. While this method has been beneficial, it still has limitations. When more than one target is detected, it is not possible to determine the primary source of fecal contamination. In this study, a nonhost specific target was used to normalize MST results, and standard curves were created to relate gene copies of the target to the equivalent dry weight of feces. The dry weight of feces can then be compared to determine the primary source of contamination. These standards were applied to MST results from five beaches in Macomb County, MI.