In a collaborative study with the Illinois State Geological Survey, groundwater samples have been collected since 1996 near two swine confinement facilities (site A and site C) that use lagoons for manure storage and treatment to assess the impact of manure management on groundwater quality. Several key contaminant indicators, including inorganic ions, antibiotics, and antibiotic resistance genes and bacteria, were analyzed in groundwater collected from 23 monitoring wells. Chloride, ammonium, potassium, and sodium were predominant constituents in the manure samples and served as indicators of groundwater contamination. Based on analysis of these constituents, shallow groundwater has been impacted by lagoon seepage at both sites. The extent of migration of contaminants down gradient from the lagoons and the magnitude of contaminant concentrations in groundwater were significantly greater at site A than at site C. Migration of contaminants was generally 30 to 150 meters down gradient of the lagoons at site C and A, respectively, and can be attributed to the difference in the local geologic conditions at the sites.

Bacterial tetracycline resistance genes served as distinct genotypic markers to indicate the dissemination and mobility of antibiotic resistance genes that originated from the lagoons. Applying PCR to genomic DNA extracted from the lagoon and groundwater samples, four commonly occurring tetracycline (tet) resistance genes, tet(M), tet(O), tet(Q), tet(W), were detected. The frequency of detection of the four tet genes in groundwater samples from site A indicated fluctuating resistance gene patterns over time and across the groundwater flow path. In contrast to site A where persistence of tet genes occurred in most well samples, there were significant periodic differences in tet gene occurrence in groundwater from site C. In 2001, tet genes were below detection in nearly all groundwater samples, while in 2003, tet genes were detected in nearly all samples. The detection frequency of tet genes was much higher in wells located closer to and down gradient from the lagoons than in wells more distant from the lagoons. Also, in 2003, higher frequencies of tet genes occurred in background wells located up-gradient from the lagoons at both sites. Further analysis using quantitative PCR methods demonstrated that in lagoon samples tet(Q), relative to the total bacteria present, was much greater than tet(M). These results suggest that in the groundwater underlying both facilities, tetracycline resistance genes exist and are somewhat persistent, but the distribution and potentially the flux for each tet gene varied throughout the study period.

Available Publications

Krapac, I.G., Koike, S., Meyer, M.T., Snow, D.D., Chou, S.F.J., Mackie, R.I., Roy, W.R., and Chee-Sanford, J.C., 2004, Long term monitoring of the occurrence of antibiotics residues and antibiotic resistance genes in groundwater near swine confinement facilities: in Proceedings of the 4nd International conference on pharmaceuticals and endocrine disrupting chemicals in water, Minneapolis, Minn., National Ground Water Association, October 13-15, 2004, CD-ROM, p. 158-174.

More Information

• Project contact: Mike Meyer