Swine Lagoon Effluent as a Potential Source of Antibiotic Resistant Genes in Surface Water.

The use of antibiotics in animals is suspected to be a major route of the transference of antibiotic resistant bacteria to humans, even when different antibiotics are used in animals than in people.   North Carolina is the home of our Nation’s second largest swine industry.  Most of this swine production is restricted to a small geographical area in southeastern North Carolina. This high concentration of swine production may increase the risk of antibiotic resistant bacteria from swine operations reaching the nearby surface waters.   The goal of this study is to identify and quantify E. coli isolates with  antibiotic resistant genes in raw swine manure, lagoon effluent from a commercial swine facility and in nearby  ground and surface waters. To date, 900 E. coli strains from swine manure, lagoon effluent and nearby ground and surface waters have been recovered for the purpose of evaluating for antibiotic resistance genes and the phenotypic expression of the resistance.  E. coli isolates have been evaluated for the phenotypic expression of antibiotic resistance to various concentrations of the following antibiotics: erythromycin, neomycin, oxytetracycline, streptomycin, tetracycline, cephalothin, apramycin, sulfamethoxazole, and trimethoprim-sulfamethoxazole.  One hundred percent of the E. coli isolates displayed multiple antibiotic resistances.  Genotypic evaluation for antibiotic resistance genes (aadA, strA, strB, tetA, tetB, tetC, sul1, sul2, sul3, and aac(3)IV) in the E. coli isolates is underway.  The distribution of antibiotic resistant genes in swine-manure derived bacteria in shallow groundwater near the stream or in the stream would document the need for improved mitigation strategies.