Detection of escherichia coli in northern Lake Michigan waters using qpcr method c
The defined substrate method, Colilert® (IDEXX, Westbrook, ME), is currently the most widely used method approved by the United States Environmental Protection Agency (US EPA) to detect Escherichia coli and total coliforms in surface water. One use for the test is to determine the risk of exposure to waterborne pathogens by beach users after contact with recreational water. However, results are not available until 18 to 24 hours after sampling because the microbiological cultures need to incubate. This could mean beach goers could be exposed to contaminated water while lab testing proceeds. To help alleviate this shortcoming the US EPA has recently investigated a quantitative polymerase chain reaction (qPCR) method for use in recreational waters. This qPCR method is called Method C (US EPA, 2015) and can reduce the analysis time to four hours when identifying E. coli DNA. My overall goal was to determine how qPCR Method C compares to traditional culture-based enumeration methods at Lake Michigan beaches. I conducted a comparison of both techniques (Method C and Colilert®) at six beaches in Door, Kewaunee, and Manitowoc counties in Wisconsin throughout the 2016 and 2017 summer beach seasons. Six beaches were selected and placed in three groups: high, moderate and low mean E. coli concentrations based on Colilert® historical data since 2003. More than 30 sampling events for each beach were used to help elucidate relationships between these two methods. My work will provide critical knowledge for beach management as practitioners consider a transition to a rapid qPCR method for E. coli detection.
Water quality management