Antibiotic-resistant pathogens in the Blue Marsh Watershed: Superbugs isolated from water and sediment in Reading, Pennsylvania

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Jill M. Felker, Environmental Studies, Antioch New England, Keene, NH, Melissa Buchter, Safitaj Sindhar and Tami Mysliwiec, Penn State Berks, Reading, PA

Background/Question/Methods
Anthropogenic activities in and around waterways impact the microscopic ecosystem and threaten human health. Selective pressures, such as emerging contaminants and nonpoint source pollution, enable microbial communities to evolve antibiotic-resistant characteristics. Watersheds collect chemicals and pollutants in surface water, groundwater, and sediment. Some chemical pollutants are biochemically similar to certain antibiotics and create conditions that allow for the evolution of antibiotic-resistant bacteria. Antibiotic-resistant organisms that demonstrate resistance to more than one antibiotic are known as superbugs. This study aimed to evaluate the microbial antibiotic-resistant organisms in three sites adjacent to human recreational, agricultural, and industrial activities. Water and sediment were collected monthly for one year. Escherichia coli and Enterococci spp. counts were collected using membrane filtration procedures, following the manufacturer's recommendations. Kirby Bauer disk diffusion methodology was used to determine antibiotic susceptibility of six classes of antibiotics in approximately 10% of the isolated colonies found in the collected samples. In this study, standard clinical antibiotic concentrations prescribed to treat infections in humans were utilized to gauge the risk to individuals using the waterways. Antibiotic-resistant genes were identified from genomic DNA samples using PCR analysis.
Results/Conclusions
Approximately 89% of the E.coli cultures tested from the Blue Marsh watershed samples were resistant to at least one antibiotic. Around 52% of the isolates tested were resistant to two or more antibiotics. Similar findings were found for Enterococci, with 69% of the cultures resistant to one antibiotic and 40% of the isolates resistant to multiple antibiotics. Ampicillin and tetracycline resistance were common throughout the Blue Marsh watershed. PCR analysis uncovered tetracycline-resistant genes, tet(A) and tet(R), in genomic DNA samples. Both tet(A) and tet(R) resistance genes are common in microbial communities exposed to emerging contaminants. Results suggest human activities may influence antibiotic resistance in microbial communities, exposing those using the Blue Marsh watershed to pathogenic superbugs.