356-12 Antibiotic-Resistant Fecal Bacteria in Urban Floodwaters of Charleston, SC

Abstract:

Rapid urbanization in coastal areas, combined with intense precipitation events and climate-change-driven coastal flooding, poses an existential challenge for many coastal communities. Floodwater in coastal urban areas contains nonpoint-source pollutants, but antibiotic-resistant fecal coliforms pose an additional threat to human health. In this study, floodwater samples from tidal and rainfall events were collected at multiple locations on the Charleston peninsula: some sites were affected by both tidal and rainfall flooding, and another 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, turbidity, coliforms, and E. coli. Coliforms and E. coli were also tested for antibiotic resistance to amoxicillin, ampicillin, and augmentin.  Antibiotics are 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 elevated concentrations of chemical contaminants and high counts of 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. Among the antibiotics tested, coliforms and E. coli were the least resistant to augmentin. Augmentin, which includes amoxicillin and clavulanic acid (a beta-lactamase inhibitor), was expected to inhibit bacterial defense mechanisms, and the data supported it. A positive correlation was observed between the percent coverage of impervious surfaces and coliform counts at all 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 increase the prevalence of antibiotic-resistant bacteria in floodwater generated by rainfall and tidal flooding in coastal cities like Charleston.

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