Institute: South Dakota
Year Established: 2015 Start Date: 2015-03-01 End Date: 2016-02-29
Total Federal Funds: $20,000 Total Non-Federal Funds: $40,000
Principal Investigators: Linda DeVeaux, Lisa Kunza
Abstract: Bacterial levels, particularly fecal coliforms such as Escherichia coli, are standard water quality indicators of fecal contamination. The EPA estimates that 25% of national groundwater systems exceed the Total Coliform Rule, suggesting a widespread dissemination of enteric organisms into the environment . South Dakota surface water is not immune to fecal contamination, and according to the 2014 South Dakota Integrated Report for Surface Water Quality Assessment, sections of Rapid Creek are affected by unacceptably high levels of indicator bacteria, particularly E. coli . Routine testing provides a snapshot of microbial abundance and content; however, such sampling does not take into account the pathogenic profile of the bacteria. Certain E. coli strains are commensal organisms that are part of the normal microflora of the human intestinal tract, and when ingested do not have any adverse health effects. However,infection by pathogenic variants, particularly Shiga-toxigenic E. coli serotype O157:H7, accounts for approximately 73,000 annual cases of reported illnesses in the U.S. alone . Such strains are considered emerging zoonotic infectious agents, and have been linked to outbreaks of severe diarrhea and hemolytic uremic syndrome, an often lethal condition in small children. Though disease-causing in humans, many of the pathogenic E. coli strains are common inhabitants of the guts of both domestic and wild animals, particularly ruminants, where they appear to cause no symptoms. Cattle are the major reservoir of Shiga toxin-producing E. coli(STEC), and transmission to humans often occurs through fecally-contaminated water sources. The ability of E. coli to cause disease is directly related to its genetic make-up, and ‘horizontal gene transfer’ is a source of evolution that allows genes to be passed easily between even distantly related species of bacteria. Shiga-toxigenic E. coli possess a gene for Shiga toxin,a virulence factor that contributes to the disease-causing potential. The Shiga toxin geneoriginated in Shigella dysenteriae, and has been found in Enterobacter, Citrobacter, Acineobacter, Campylobacter, and Hamitonella bacterial species . Since horizontal gene transfer has been observed where bacterial levels are high, it is expected that the number of copies of pathogenic genes will increase as they are shared between individuals. The more potentially harmful genes a bacterium acquires, the more likely it will be to cause disease. Both municipal drinking water and water used recreationally are known to harbor Shiga toxin-producing organisms, and have been linked to a number of STEC outbreaks. There are two antigenically distinct Shiga toxin variants: the highly conserved Stx1, and the more diverse Stx2, which has five subtypes (stx2, stx2c, stx2d, stx2e, and stx2g) and 11 variants. Other known virulence factors often carried in tandem with the Shiga toxins include heat-labile and heat-stable toxins, verotoxins, cytotoxic necrotizing factors, attaching and effacing mechanisms, enteroaggregative mechanisms and enteroinvasive mechanisms . Parts of Rapid Creek have fecal coliform impairment due to multiple influences of the sewage treatment plant, septic tanks, and cattle. We propose to apply common molecular biology techniques to create a genetic fingerprint of Shiga-toxin and related pathogenicity genes at 6 predetermined points along Rapid Creek from Canyon Lake to the Cheyenne River. Samples will be collected twice--once after spring run-off and once at the low end of summer flows. Finally, we will collect potential source samples, including livestock or wildlife feces, sewage intake samples, and septic tank sludge. Our goal is to establish a unique profile for each sample that will indicate the source(s) of contamination. The information generated by this project could lead to guidance for implementation of new best management practices for these watersheds.