Date of Award

Fall 2022

Document Type

Open Access Dissertation


Environmental Health Sciences

First Advisor

Geoffrey I. Scott


The Southeastern coastal plain is the most rapidly urbanizing region in the United States. Associated landscape changes which increase imperviousness lead to hydrological cycle alterations, increasing runoff of nonpoint source (NPS) pollution. Urban and agricultural NPS runoff is generally discharged into stormwater ponds, which sequester chemical contaminants, nutrients, and microbes to reduce loading into coastal ecosystems. Studies of these ponds have indicated elevated levels of trace metals, antimicrobial compounds, and bacterial contamination (SCSGC 2018).

Interactions of aquatic pathogens Vibrio vulnificus and Enterococcus faecium with trace metals (arsenic, copper, zinc) and clinically relevant antimicrobials (triclosan, ciprofloxacin, oxytetracycline) commonly found in coastal ponds and estuaries were examined to determine how they may affect growth and impact antimicrobial resistance. Both species have significant environmental and public health significance in terms of water quality, seafood safety and contact recreation. Experimental data indicate that binary mixtures of environmentally relevant concentrations of some antimicrobials and metals inhibit growth in V. vulnificus and E. faecium. A mixture of copper and oxytetracycline is of note due to a biostimulatory effect at levels a dose 60% lower than the copper Effects Range Low (ERL) sediment quality guideline and at the Probable No-Effect Concentration (PNEC) of oxytetracycline. This dose combination also resulted in susceptibility changes to three clinically relevant antibiotics of different classes.


© 2022, Cassandra L. Horton