Tre’Shur Williams-Carter expects she’ll find antimicrobial resistance in the Oconee River in Athens. That’s because AMR—the adaptation that makes infections from bacteria, fungi and viruses difficult to treat—is common in urban streams like those in the Upper Oconee Watershed.

But, by collecting both running river water and the biofilm coating rocks on the streambed, she hopes to learn more about the types of genes that lead to resistance and where they are coming from.

A master’s student at the Odum School of Ecology, Williams-Carter works with Krista Capps, a stream ecologist with a dual appointment at the Odum School and the Savannah River Ecology Laboratory.

Williams-Carter is studying the Oconee River and its tributaries to find antimicrobial resistance genes and compare how the amount of bacteria, as well as other contaminants (like caffeine and pharmaceutical products), changes among sites in the river.

She’s testing several sites in different seasons through water samples pulled directly from the stream, as well samples from the biofilm attached to rocks found in the streambed.

By scrubbing the biofilm from rocks—taking a sample of the natural, slimy matrix of organisms that accumulates and coats hard surfaces in water—Williams-Carter hopes to document a more realistic picture of AMR in the Oconee River.

“Even though biofilms are incredibly common in freshwater ecosystems, relatively few studies have examined the presence of AMR in biofilm communities in river networks,” she said.

Water samples can show a snapshot of contamination—how much bacteria is in river water right now and whether that bacteria carries genes that make them resistant to antibiotics—but biofilm gives information over a longer term. 

“Using both sample types will provide a more comprehensive assessment of where antibiotic resistance genes can be found throughout the watershed,” Williams-Carter said. “Bacterial contamination, antibiotic resistance, and emerging contaminants have all been studied as separate issues in the Oconee River, but no one has looked at these in relation to each other.”

Researchers across UGA disciplines—including environmental health Professor Erin Lipp and microbiology Associate Professor Elizabeth Ottesen—have studied the Oconee River for years to learn about specific sources of antimicrobial resistance and how those lessons might apply to similar urban streams.  

“Antimicrobial resistance is a global health concern. Researchers are working to find where it comes from and how it spreads through the environment,” said Capps, associate professor of ecology. “Is it coming from wastewater treatment plants or from sewage from hospitals? Is it coming through agricultural production? We have much to learn and are trying to build the full, complicated system that describes the movement, spread and development of antimicrobial resistance.”

Studying biofilms in streams for AMR genes is a relatively novel approach, according to Capps. In addition to showing how many resistance genes are in the river, it might also provide insight about whether these genes hang around over time or wash away.

Comparing AMR across sites and habitats in streams will help us gain a better understanding of what drives antibiotic resistance in this watershed, Williams-Carter said.

“Human activities can lead to more bacteria entering streams. For example, we might see numbers drop in summer when the population dips in Athens. But warmer conditions may also increase bacteria entering water from other sources. It will be interesting to see Athens’ patterns,” she said.

“The project is about this particular river—the Oconee River—but it’s also probably representative of many other rivers. Athens, like cities all over the world, has hospitals and schools, industry and agriculture. There’s a lot going on that may contribute to patterns of AMR in the river.”

Growing up in a military family, Williams-Carter lived in Pennsylvania and Texas before finishing high school in Georgia and earning a bachelor’s degree in biology with a concentration in wildlife conservation from Fort Valley State University.

She started a master’s program at Odum School in fall 2025 as a Butler Fellow, a scholarship established by James E. Butler Jr., a Columbus attorney who gifted $1 million in 2006 to what was then the Institute of Ecology.