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A recent study published in Geohealth has shifted the focus away from pig farms to local rivers and streams as the primary source of Salmonella enterica contamination along the North Carolina coast following Hurricane Florence in 2018. This research, led by the University of Illinois Urbana-Champaign, provides vital insights into managing the spread of antibiotic-resistant pathogens after flooding events, especially in coastal areas of developing countries increasingly affected by tropical storms.
Investigating the Origins of S. enterica
The team, headed by Helen Nguyen, a professor of civil and environmental engineering, and graduate student Yuqing Mao, utilized various sequencing techniques to identify the source of S. enterica in environmental samples from coastal North Carolina. Nguyen explains the gravity of the situation, stating, “Infections caused by antibiotic-resistant pathogens are responsible for approximately 2.8 million human illnesses and 36,000 deaths per year in the U.S. alone. These infections spread easily across the globe and are a major burden on burgeoning health care systems, but they are preventable through mitigation.”
The study confronts the common assumption that wastewater sources, septic systems, and livestock farms are the main culprits in spreading antibiotic-resistant bacteria during floods. Before this study, no research had conclusively pinpointed the sources of such contamination.
Uncovering New Findings in Coastal North Carolina
Coastal North Carolina, with its high concentration of swine farms and frequent coastal flooding, served as an ideal study area. Nguyen's team collected 25 water samples from areas downstream of swine farms three weeks after Hurricane Florence. They discovered S. enterica in 23 of these samples.
Contrary to expectations, Nguyen reports, “We analyzed free-floating genetic markers—chromosomes and plasmids—using high-fidelity whole-genome sequencing and found that S. enterica in the samples collected after Hurricane Florence were not from animals or manure.” The team traced the bacteria's origin to numerous small local rivers and streams, suggesting that these pathogens are already entrenched in the natural environment.
Implications for Future Research and Policy
This finding is critical, particularly in the context of climate change, which is expected to bring warmer temperatures and possibly more frequent and intense tropical storms. Nguyen emphasizes the need for researchers and policymakers to recognize that agricultural and human wastewater are not the only sources to consider when planning to prevent the spread of pathogenic bacteria after hurricanes.
The research team is expanding their study beyond coastal areas, collaborating with other campus researchers to investigate the spread of pathogens from Canada goose feces in Illinois.
This study, involving contributions from the Carl R. Woese Institute for Genomic Biology, the Carle Illinois College of Medicine, and the University of Florida, was supported by the IGB, The Grainger College of Engineering, the Allen Foundation, and the EPA. It marks a significant step in understanding and managing the spread of antibiotic-resistant pathogens in the wake of natural disasters.