title: Antimicrobial use and resistance in swine waste treatment systems.
abstract: Chlortetracycline and the macrolide tylosin were identified as commonly used antimicrobials for growth promotion and prophylaxis in swine production. Resistance to these antimicrobials was measured throughout the waste treatment processes at five swine farms by culture-based and molecular methods. Conventional farm samples had the highest levels of resistance with both culture-based and molecular methods and had similar levels of resistance despite differences in antimicrobial usage. The levels of resistance in organic farm samples, where no antimicrobials were used, were very low by a culture-based method targeting fecal streptococci. However, when the same samples were analyzed with a molecular method detecting methylation of a specific nucleotide in the 23S rRNA that results in resistance to macrolides, lincosamides, and streptogramin B (MLSB), an unexpectedly high level of resistant rRNA (approximately 50%) was observed, suggesting that the fecal streptococci were not an appropriate target group to evaluate resistance in the overall microbial community and that background levels of MLSB resistance may be substantial. All of the feed samples tested, including those from the organic farm, contained tetracycline resistance genes. Generally, the same tetracycline resistance genes and frequency of detection were found in the manure and lagoon samples for each commercial farm. The levels of tetracycline and MLSB resistance remained high throughout the waste treatment systems, suggesting that the potential impact of land application of treated wastes and waste treatment by-products on environmental levels of resistance should be investigated further.
authors.affiliation: Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, 3204 Newmark Civil Engineering Laboratory, MC250, 205 North Mathews Avenue, Urbana, IL 61801, USA.
authors.forename: Archana
authors.initials: A
authors.lastname: Jindal
authors.forename: Svetlana
authors.initials: S
authors.lastname: Kocherginskaya
authors.forename: Asma
authors.initials: A
authors.lastname: Mehboob
authors.forename: Matthew
authors.initials: M
authors.lastname: Robert
authors.forename: Roderick I
authors.initials: RI
authors.lastname: Mackie
authors.forename: Lutgarde
authors.initials: L
authors.lastname: Raskin
authors.forename: Julie L
authors.initials: JL
authors.lastname: Zilles
mesh_terms: D000822:Animal Husbandry / Q000379:methods*; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000494:pharmacology; D001414:Bacitracin / Q000008:administration & dosage / Q000494:pharmacology; D002751:Chlortetracycline / Q000008:administration & dosage / Q000494:pharmacology; D003247:Conservation of Natural Resources / Q000379:methods; D024881:Drug Resistance, Bacterial; D005243:Feces / Q000382:microbiology; D008372:Manure / Q000382:microbiology*; D012037:Refuse Disposal / Q000379:methods*; D013291:Streptococcus / Q000187:drug effects / Q000302:isolation & purification; D013552:Swine
chemical_list: D000900:Anti-Bacterial Agents; D008372:Manure; D001414:Bacitracin; D002751:Chlortetracycline