title: Impact of treatment strategies on cephalosporin and tetracycline resistance gene quantities in the bovine fecal metagenome.
abstract: The study objective was to determine the effects of two treatment regimens on quantities of ceftiofur and tetracycline resistance genes in feedlot cattle. The two regimens were ceftiofur crystalline-free acid (CCFA) administered to either one or all steers within a pen and subsequent feeding/not feeding of therapeutic doses of chlortetracycline. A 26-day randomized controlled field trial was conducted on 176 steers. Real-time PCR was used to quantify bla(CMY-2), bla(CTX-M), tet(A), tet(B), and 16S rRNA gene copies/gram of feces from community DNA. A significant increase in ceftiofur resistance and a decrease in tetracycline resistance elements were observed among the treatment groups in which all steers received CCFA treatment, expressed as gene copies/gram of feces. Subsequent chlortetracycline administration led to rapid expansion of both ceftiofur and tetracycline resistance gene copies/gram of feces. Our data suggest that chlortetracycline is contraindicated when attempting to avoid expansion of resistance to critically important third-generation cephalosporins.
authors.affiliation: Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Neena
authors.initials: N
authors.lastname: Kanwar
authors.affiliation: 1] Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA [2].
authors.forename: H Morgan
authors.initials: HM
authors.lastname: Scott
authors.affiliation: Department of Large Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Norby
authors.affiliation: Department of Animal and Food Sciences, College of Agriculture and Natural resources, Texas Tech University, Lubbock, TX 79409, USA.
authors.forename: Guy H
authors.initials: GH
authors.lastname: Loneragan
authors.affiliation: Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Javier
authors.initials: J
authors.lastname: Vinasco
authors.affiliation: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Cottell
authors.affiliation: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Gabhan
authors.initials: G
authors.lastname: Chalmers
authors.affiliation: Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Muckatira M
authors.initials: MM
authors.lastname: Chengappa
authors.affiliation: Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
authors.forename: Jianfa
authors.initials: J
authors.lastname: Bai
authors.affiliation: Department of Pathobiology, Ontario Veterinary College, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
authors.forename: Patrick
authors.initials: P
authors.lastname: Boerlin
mesh_terms: D000818:Animals; D001419:Bacteria / Q000187:drug effects / Q000235:genetics*; D001424:Bacterial Infections / Q000188:drug therapy* / Q000235:genetics / Q000662:veterinary; D002417:Cattle; D002511:Cephalosporins / Q000008:administration & dosage*; D002751:Chlortetracycline / Q000008:administration & dosage; D005243:Feces / Q000382:microbiology; D054892:Metagenome / Q000187:drug effects* / Q000235:genetics; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D013753:Tetracycline Resistance / Q000187:drug effects / Q000235:genetics*
chemical_list: D002511:Cephalosporins; D012336:RNA, Ribosomal, 16S; C053503:ceftiofur; D002751:Chlortetracycline