Enteric Virus Surveillance and Microbial Source Tracking in Fresh and Marine Waters of the Seattle Area
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University of Washington Abstract Enteric Virus Surveillance and Microbial Source Tracking in Fresh and Marine Waters of the Seattle Area Elena Jaffer Chair of the Supervisory Committee: Dr. John Scott Meschke Department of Environmental and Occupational Health Sciences Introduction: (Part I.) Bacterial indicators, including fecal coliforms, E. coli, and Enterococci, serve as long-standing measures of fecal contamination. However, coliphages hold promise as viral indicators, which may be more representative of viral enteric pathogens. Filtration and concentration of large water sample volumes (i.e. 20 L) increases viral detection sensitivity. (Part II.) Poverty Bay spans 11 shoreline miles of Puget Sound west of Des Moines. In response to recent geoduck bed closures in the area, we performed a microbial source delineation study in 5 creeks upland from the Bay with the intent of discovering the source of fecal contamination. Methods: (I.) Using the Bag-Mediated Filtration System (BMFS), followed by PEG precipitation and Vertrel XF extraction, we quantified levels of enteric viruses (AdV, NoV, EnV) and male-specific coliphage (MSC) at Green Lake, Lake Washington, and Puget Sound recreational beaches during June-November 2016. MSC was enumerated using the double agar layer, and enteric viruses were detected with qPCR. These data were compared to MPN estimates for traditional fecal indicator bacteria, using Colilert®-18 and Enterolert® substrates sealed in QuantiTrays®/2000. (II.) Coliscan Easygel ® kits were used during September 2016 – May 2017 to estimate E. coli levels in 5 streams upland of Poverty Bay during wet and dry weather conditions. Results: (I.) Throughout the sampling period (n = 6-7 samples/site), detection of MSC occurred only following a wet weather event, at levels of 19 PFU/L (Matthews Beach) and 21 PFU/L (Carkeek Beach). No pathogenic enteric viruses were detected with qPCR throughout the sampling period. However, a number of indicator bacteria samples exceeded U.S. EPA and Washington State standards during the sampling period. (II.) E. coli levels across the Poverty Bay drainage basin led to identification of potential hotspots on the 5 upland creeks. Significance: Unique to the Seattle Area, this study provides an overview of bacterial indicator, coliphage, and enteric virus levels in both fresh and marine waters. In addition, it contributes to the body of literature that evaluates the potential of coliphages to more accurately indicate fecal contamination than traditional bacterial indicators.
- Environmental health