This past week’s One Health Intellectual Exchange Group’s topic focusing on microbial source tracking in bodies of water was presented by Dr. Jill Stewart. As an Assistant Professor in the Department of Environmental Sciences and Engineering at the University of North Carolina, Dr. Stewart develops techniques to detect and track pathogens in water. Dr. Stewart’s current research projects involve water quality evaluation associated with land application of waste products and water quality evaluation associated with urbanization on watersheds. Her work with environmental sciences show how environmental impacts can affect human health.
During the presentation, Dr. Stewart addressed the following learning objectives:
- Name a standard indicator used to detect fecal pollution of surface waters.
- List three issues associated with the use of traditional fecal indicator bacteria to monitor water quality.
- Define microbial source tracking and name a marker that can be used to track human-source pollution in water.
- Describe how microbial source tracking can be used to mitigate water pollution.
The presentation began with an introduction on microbial pollution and microbial detection. Dr. Stewart works with bacteria, viruses, and protozoa. Microbial pollution on water and shellfish include various sources such as waste water treatment plants, marinas, wild and domestic animals, recreational use, and food (for example, oysters). In order to detect the microbes, membrane filtration is performed and fecal coliform colonies are analyzed. This technique is widely used; however, there are some drawbacks. Disadvantages include time (it takes about twenty-four hours to complete), type of pathogen (it only works for bacteria), and determination of contamination source. Microbial Source Tracking (MST) is the method to determine fecal pollution in water sources. Molecular techniques such as PCR and assays are also incorporated. Markers of fecal microorganisms are used for analysis. Fecal indicator bacteria includes Escherichia coli. Depending on the presence of markers, fecal pollution can be linked to land development or other human causes.
The remaining of the presentation focused on two of Dr. Stewart’s studies. One of Dr. Stewart’s studies was conducted at Jordan Lake. The purpose of the study was to determine storm water and land use effects on microbial contamination. Water samples were collected at various types of area uses and different storm times. The fecal indicator bacteria were compared at a regulatory threshold, and the markers used were Bacteroides sp. (HuBac) and Methanobrevibacter smithii (nifH). There was a positive correlation between land development and microbial contamination. Storms had more of a contaminant load, and loading occurred over the course of the storm. Therefore, there was no difference in loading between dry conditions and stormy conditions.
A second study discussed by Dr. Stewart concerned fecal indicator bacteria and swine farms. Eastern North Carolina has most of the state’s swine operations, and North Carolina is the nation’s second largest state in swine production. To control swine fecal waste, common applications are swine lagoons and spraying fields. Again, Dr. Stewart found that there were higher levels of fecal indicator bacteria with rain. Swine genetic markers analyzed included pig-1-BAC, pig-2-BAC, and pig-BAC-2. The markers pig-1-BAC and pig-2-BAC were found to be correlated with pig waste.
In addition to her studies within North Carolina, Dr. Stewart also collaborates with researchers in the Galápagos Islands. A few studies were conducted by measuring water quality around sewage pipes, which emptied into the ocean. The water treatment plants also had fecal indicator bacteria. Dr. Stewart along with students will continue research in the Galápagos Islands.
The presentation concluded with Dr. Stewart stressing that single-sample monitoring for water sources may be inadequate, and alternative indicators may be necessary. These points are exemplified in her studies with land use and water contamination as well as storm water affects on water contamination. Her presentation and studies support the One Health concept connecting environmental health and human health.
Discussion and questions followed the presentation. Questions included the following topics:
- The affect of tides and timing on the analysis of storm water leaving sewage pipes in the Galápagos Islands
- Analyzing antibiotics directly in samples
- Water pollution by tour boats in the Galápagos Islands
- Collaborative work with Engineers Without Borders in the Galápagos Islands
- The difference between indicators and pathogens
- Costs for molecular techniques
- The use of caffeine as an indicator
Post Authored by Erin Beasley
NC State University