Comparison of qPCR and traditional beach monitoring methods at select Great Lakes beaches and the impact on beach management

Campbell A, Kleinheinz G. 2020. Comparison of qPCR and traditional beach monitoring methods at select Great Lakes beaches and the impact on beach management. Lake Reserv Manage. XX:XXX-XXX. The US EPA has adopted numerous techniques for enumerating fecal indicator bacteria, each with advantages and disadvantages. Traditional methods require 18 to 24 h of incubation and do not provide results in time to adequately protect public health. New rapid quantitative polymerase chain reaction (qPCR) methods have emerged. Some initial studies of these rapid methods have shown them to correlate with results from culture-based methods, accurately predicting risk for gastrointestinal illness. However, there are few comparative studies that have been conducted in the Great Lakes at beaches that are not directly impacted by human fecal contributions. In this study, Enterococcus qPCR Method 1609 and Escherichia coli qPCR Method C were compared to the defined substrate methods Enterolert and Colilert, respectively, at 4 beaches on Lake Michigan. Results suggest that no one size fits all for these methods, and each beach behaves very differently depending on the microbiological method chosen. Additionally, we investigated the management impact of changing methods using current regulatory standards. If adopted as the regulatory method, qPCR Method 1609 would result in a minimum increase of beach exceedances (advisories and closures) of 17% and a maximum increase of 43%. Likewise, E. coli Method C has a minimum increase of beach exceedances of 27% and a maximum increase of 47%. This suggests that qPCR may be more protective of public health than current culture-based enumeration methods. The increases in beach closures may have significant ramifications in local communities. This study suggests that new qPCR methods may have a role in replacing current methods, but a site-specific evaluation should be conducted before they are adopted.