Limitations and Advantages to the Application of qPCR Technologies to Determine Host Contributions of Fecal Indicator Bacteria in Stormwater
Current methods of quantification of fecal indicator bacteria (FIB) are based on culturing techniques. These tests generally take twenty-four hours to complete and offer no information to identify potential host sources. Results from these culturing techniques can be ambiguous when deployed in stormwater source tracking efforts to remediate FIB pollution.
A series of new genetic based methods have been developed to answer the need for more rapid and specific techniques to measure FIB. Most prominent of these are the newly approved US-EPA Methods for the determination of Enterococci and Bacteroides by TaqMan quantitative polymerase chain reaction (qPCR). Additionally, a number of qPCR methods have been recently published which can identify and quantify genetic material from host specific fecal bacteria. This is accomplished by identifying genetic sequences unique to fecal bacteria in certain hosts. The use of these assays can be very powerful in identifying organisms contributing to a FIB load within a watershed or drainage area when used as part of a weight of evidence approach incorporating traditional water quality tracers and nontraditional chemical tracers. However, genetic variability in the bacterial populations, host cross over, bacterial longevity and viability, and other factors can complicate the interpretation of their results. This talk will highlight some of the pitfalls and successes in employing these tools in several sub-watershed based microbial source tracking projects.