|Chee Sanford, Joanne|
Submitted to: American Society for Microbiology Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: 12/6/2001
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: Over 80% of all swine producers in the U.S. routinely use antibiotics in feed as prophylactics and growth promoters. Swine effluent, containing antibiotics, is generally applied to cropland as a fertilizer and waste disposal strategy. These practices may increase the diversity and occurrence of antibiotic resistance genes in agricultural soils. Soil samples were collected from several Illinois hog farms before and after effluent application, and from fields with histories of no effluent application. Bacteria from these samples were cultivated on unamended MR2A medium and MR2A media amended with the feed additives bacitracin, chlortetracycline, tetracycline and tylosin to assess the prevalence of organisms with resistant phenotypes. Further testing of particular isolates was done to identify multiple drug resistant organisms. DNA extracted from the soil samples was purified and evaluated by PCR for the presence of 20 tetracycline resistance genes, coding for ribosomal protection proteins (RRPs) and efflux pumps. Effluent application appeared to increase the occurrence of tetracycline resistance determinants, particularly the RPP genes tet (M) and tet (Q). Cultivation of bacteria revealed that soils with a history of heavy effluent application contained greater numbers and variety of resistant bacteria than soils with no history of effluent application. Isolates from manured soils exhibited resistance to the multiple antibiotics ampicillin, bacitracin, chloramphenicol, chlortetracycline, erythromycin, kanamycin, streptomycin and tetracycline. Results indicate that the pool of antibiotic resistance genes in agricultural soils may increase temporarily after of effluent application from animals consuming antibiotics.