Effects of chlortetracycline and copper supplementation on the prevalence, distribution, and quantity of antimicrobial resistance genes in the fecal metagenome of weaned pigs.
Use of in-feed antibiotics such as chlortetracycline (CTC) in food animals is fiercely debated as a cause of antimicrobial resistance in human pathogens; as a result, alternatives to antibiotics such as heavy metals have been proposed. We used a total community DNA approach to experimentally investigate the effects of CTC and copper supplementation on the presence and quantity of antimicrobial resistance elements in the gut microbial ecology of pigs. Total community DNA was extracted from 569 fecal samples collected weekly over a 6-week period from groups of 5 pigs housed in 32 pens that were randomized to receive either control, CTC, copper, or copper plus CTC regimens. Qualitative and quantitative PCR were used to detect the presence of 14 tetracycline resistance (tet) genes and to quantify gene copies of tetA, tetB, blaCMY-2 (a 3rd generation cephalosporin resistance gene), and pcoD (a copper resistance gene), respectively. The detection of tetA and tetB decreased over the subsequent sampling periods, whereas the prevalence of tetC and tetP increased. CTC and copper plus CTC supplementation increased both the prevalence and gene copy numbers of tetA, while decreasing both the prevalence and gene copies of tetB. In summary, tet gene presence was initially very diverse in the gut bacterial community of weaned pigs; thereafter, copper and CTC supplementation differentially impacted the prevalence and quantity of the various tetracycline, ceftiofur and copper resistance genes resulting in a less diverse gene population.
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
Getahun E
GE
Agga
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA. Electronic address: hmscott@cvm.tamu.edu.
H Morgan
HM
Scott
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
Javier
J
Vinasco
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
T G
TG
Nagaraja
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
Raghavendra G
RG
Amachawadi
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
Jianfa
J
Bai
Department of Large Animal Clinical Sciences, Michigan State University, East Lansing, MI 48824-1413, USA.
Bo
B
Norby
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
David G
DG
Renter
Department of Diagnostic Medicine and Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, KS 66506, USA.
Steve S
SS
Dritz
Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506, USA.
Jim L
JL
Nelssen
Department of Animal Sciences and Industry, College of Agriculture, Kansas State University, Manhattan, KS 66506, USA.
Mike D
MD
Tokach
D000821:Animal Feed / Q000032:analysis; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage / Q000494:pharmacology*; D002511:Cephalosporins / Q000494:pharmacology; D002751:Chlortetracycline / Q000008:administration & dosage / Q000494:pharmacology*; D003300:Copper / Q000008:administration & dosage / Q000494:pharmacology*; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements / Q000032:analysis; D024881:Drug Resistance, Bacterial; D000069196:Gastrointestinal Microbiome / Q000187:drug effects*; D008297:Male; D016133:Polymerase Chain Reaction / Q000662:veterinary; D011897:Random Allocation; D012641:Selection, Genetic; D034421:Sus scrofa / Q000382:microbiology*
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D003300:Copper; D002751:Chlortetracycline
Antimicrobial resistance; Antimicrobial resistance gene quantification; Chlortetracycline; Copper; Pigs; Total community DNA