A NASA image containing visible and infrared data shows the presence of dissolved organic matter, including potential antibiotic pathogens, in North Carolina's coastal waterways following Hurricane Florence. The study overturns previous ideas about the source of salmonella contamination in North Carolina, pointing the finger at rivers and streams rather than hog farms and calling for revised disease control strategies.
Local rivers and streams were the source of Salmonella Enteritidis contamination in coastal North Carolina after Hurricane Florence in 2018, rather than the region's large number of pig farms as previously suspected, researchers report in the journal Geohealth.
Impact on disease control
These findings have important implications for controlling the spread of disease caused by antibiotic-resistant pathogens after flooding events, especially in coastal areas of developing countries that are severely affected by an increase in tropical storms.
The study, led by Helen Ruan, a professor in the Department of Civil and Environmental Engineering at the University of Illinois at Urbana-Campaign, and Yuqing Mao, a graduate student, used genetic tracking technology to track the presence and origin of Enterobacteriaceae in environmental samples from coastal North Carolina.
"Infections caused by antibiotic-resistant pathogens cause approximately 2.8 million illnesses and 36,000 deaths each year in the United States alone," Nguyen said. "These infections spread easily across the globe and are a major burden on rapidly growing healthcare systems, but they are preventable by mitigating them."
Research results and methods
Because genetic markers of human and animal feces are often found in floodwaters, wastewater sources, septic systems and livestock farms are often blamed for spreading antibiotic-resistant bacteria and genetic material into the environment, the study notes. However, there are no known studies that have conclusively determined the source point of the contaminants.
"Coastal North Carolina is a good case study area because it has a large number of hog farms and private septic systems, and coastal flooding from tropical storms is fairly common," Nguyen said.
Three weeks after Hurricane Florence, Nguyen's team collected 25 water samples from water bodies downstream of pig farms in North Carolina's agricultural production areas, and 23 of them contained enterovirus bacteria.
The researchers used high-fidelity whole-genome sequencing to analyze free-floating genetic markers -- chromosomes and plasmids -- and found that the Enterococcus enteritidis in samples taken after Hurricane Florence did not come from animals or feces. The team genetically traced the origins of the bacteria to many small local rivers and streams, meaning the pathogens have already established themselves in the natural environment.
Broad context of the study and future research
"As climate change brings warmer temperatures—bacteria thrive in warmer environments—and the potential for larger, more frequent tropical storms, researchers and policymakers need to recognize the importance of our findings," Nguyen said. "Agricultural and human wastewater should not be the only sources considered when designing hazard mitigation plans to prevent the spread of pathogens after hurricanes."
Nguyen's team plans to expand this research beyond coastal areas and is working with other campus researchers to study the spread of pathogens in Canada goose feces in Illinois.
Reference: "Local and environmental reservoirs of Salmonella Enteritidis following Hurricane Florence flooding," by Yuqing Mao, Mohamed Zeineldin, Moiz Usmani, Antarpreet Jutla, Joanna L. Shisler, Rachel J. Whitaker, and Thanh H. Nguyen, November 3, 2023, GeoHealth.
doi:10.1029/2023gh000877
Compiled source: ScitechDaily