Rapid Response: Application of a qPCR-Based Test for Enterococci and Human-Associated Bacteroides as a Rapid Beach Management Tool in Hawai‘i.
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2017-12
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Climate change is projected to increase the risk of loss for people, assets, economies and ecosystems, as extreme weather events, such as tropical storms and hurricanes, will increase in number and intensity. Changing climate and urbanization will alter inputs of fecal bacteria in the environment which can compromise the health of Hawai’i residents and visitors. One problem we face regarding fecal bacteria in the environment is the inadequacy of the existing methods to detect their presence and numbers quickly enough to be able to warn swimmers about contaminated water. Currently used culture-based microbial detection methods take a minimum of 24 hours to complete, while newer rapid molecular methods, can be completed in a few hours. Hawai’i is extremely well suited for the application of these rapid methods due to the small land mass, high population density and high numbers of visitors to the islands. Unfortunately, no validated and ready to use in Hawai’i rapid method exists. Our preliminary studies identified several critical problems with the rapid methods that are specific to Hawai’i and likely to other tropical regions. One of the problems is the high background levels of enterococci from non-human sources found in Hawai’i’s nearshore waters that could lead to beach warnings being posted when no actual sewage contamination, and related health hazard, exists. This could negatively impact public perception of Hawaii' beaches, and our hence the state's tourism industry.
The goal of this project was to improve water quality management decisions in the state by 1) optimizing a rapid qPCR-based method for enterococci in Hawai’i, and 2) implementing a new qPCR-based method for human-associated Bacteroides (HBAC) as a sewage tracer to use in parallel with the EPA recommended enterococcus tests. If the HBAC assay can be validated as an adjunct to the enterococcus method it could be a way of generating faster results. This could help to improve the accuracy of and speed up beach management decisions (whether to post beach advisories).
Based on analyses of pure fecal samples collected from humans and several animals in Hawai’i, this project identified that the human specificity of HBAC HF183 is 74% and sensitivity 100%. The HBAC HF183 marker was detected in all untreated wastewater samples we collected at concentrations which exceeded enterococci’s by approximately four orders of magnitude, indicating that it should be easily detected when sewage-borne enterococci are present. Correlation coefficient and Index of Agreement determined between the traditional cultivation-based method and the modified, more rapid, molecular method for enterococci examined by this project, met EPA's requirements for alternative methods (R2=0.76 and IA=0.78) regarding how closely they matched the approved method. During our study, samples were routinely collected, analyzed and results reported within three hours. By implementing HBAC as a sewage tracer and by optimizing the enterococcus molecular-based method, more accurate and faster recreational water quality assessment will be possible. It is anticipated that, if adopted by the state the molecular method will positively affect reduce the rate of sewage-borne illness and related costs.
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