Soil-borne reservoirs of antibiotic-resistant bacteria are established following therapeutic treatment of dairy calves.
We determined if antibiotics residues that are excreted from treated animals can contribute to persistence of resistant bacteria in agricultural environments. Administration of ceftiofur, a third-generation cephalosporin, resulted in a ∼ 3 log increase in ceftiofur-resistant Escherichia coli found in the faeces and pen soils by day 10 (P = 0.005). This resistant population quickly subsided in faeces, but was sustained in the pen soil (∼ 4.5 log bacteria g(-1)) throughout the trial (1 month). Florfenicol treatment resulted in a similar pattern although the loss of florfenicol-resistant E. coli was slower for faeces and remained stable at ∼ 6 log bacteria g(-1) in the soil. Calves were treated in pens where eGFP-labelled E. coli were present in the bedding (∼ 2 log g(-1)) resulting in amplification of the eGFP E. coli population ∼ 2.1 log more than eGFP E. coli populations in pens with untreated calves (day 4; P < 0.005). Excreted residues accounted for > 10-fold greater contribution to the bedding reservoir compared with shedding of resistant bacteria in faeces. Treatment with therapeutic doses of ceftiofur or florfenicol resulted in 2-3 log g(-1) more bacteria than the estimated ID50 (2.83 CFU g(-1)), consistent with a soil-borne reservoir emerging after antibiotic treatment that can contribute to the long-term persistence of antibiotic resistance in animal agriculture.
Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, 99164, USA.
Jinxin
J
Liu
Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, 99164, USA.|Key Laboratory of Tropical Marine Bio-Resources and Ecology, South China Sea Institute of Oceanology, Chinese Academy of Sciences, Guangzhou, 510301, China.
Zhe
Z
Zhao
Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, 99164, USA.
Lisa
L
Orfe
Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, 99164, USA.
Murugan
M
Subbiah
Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA, 99164, USA.
Douglas R
DR
Call
D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy* / Q000382:microbiology; D002511:Cephalosporins / Q000378:metabolism / Q000494:pharmacology* / Q000627:therapeutic use; D004350:Drug Residues / Q000378:metabolism / Q000494:pharmacology; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D005243:Feces / Q000382:microbiology; D010118:Oxytetracycline / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use; D012987:Soil; D012988:Soil Microbiology; D013839:Thiamphenicol / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology / Q000627:therapeutic use
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D012987:Soil; C053503:ceftiofur; C035534:florfenicol; D013839:Thiamphenicol; D010118:Oxytetracycline