THE PRESENCE OF ANTIBIOTIC-RESISTANT E. COLI AND COLIFORMS IN URBAN FLOODWATERS OF CHARLESTON, SC

Rapid urbanization in coastal areas, combined with intense precipitation events and coastal flooding exacerbated by climate change, poses an existential challenge for many coastal communities. Floodwater in coastal urban areas contains nonpoint source pollutants, but fecal coliforms resistant to antibiotics pose an additional threat to human health. In this study, tidal and rainfall floodwater samples were collected from four Charleston, South Carolina locations - three sites were impacted by tidal and rainfall flooding, and the fourth site was affected only by tidal flooding. All sites are highly urbanized, but a green buffer surrounds the tidal flooding site. All water samples were analyzed for nutrient and trace metal contaminants, coliforms, and E. coli. Coliforms and E. coli were also tested for antibiotic resistance using Amoxicillin, Ampicillin, Augmentin, and Erythromycin. These antibiotics are all commonly prescribed for bacterial illnesses in humans and animals. This study aims to analyze antibiotic resistance patterns in coliforms as correlated to flood sources, land-use patterns, and chemical contaminants. Floodwater from all areas contained high chemical contaminants, coliforms, and E. coli. Antibiotic-resistant coliforms and E. coli were also found in all water samples. The most densely urbanized sites had the highest contamination levels, while the lone site with a green buffer had lower contamination. Coliform and E. coli concentrations correlated with rainfall, suggesting rain runoff is a primary vector for pathogen transport. Of all antibiotics, coliforms and E. coli were least resistant to Augmentin. A positive correlation was observed between the percent coverage of impervious surfaces and coliforms at all the sites. Overall, the results suggest that land-use patterns increase the prevalence of antibiotic-resistant coliforms and increase the likelihood of human exposure to these potential pathogens. Climate change is expected to exacerbate the presence of antibiotic-resistant bacteria in floodwater generated from rainfall and tidal flooding in coastal cities.