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Soil‐borne reservoirs of antibiotic‐resistant bacteria are established following therapeutic treatment of dairy calves
Author(s) -
Liu Jinxin,
Zhao Zhe,
Orfe Lisa,
Subbiah Murugan,
Call Douglas R.
Publication year - 2016
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/1462-2920.13097
Subject(s) - ceftiofur , florfenicol , biology , feces , antibiotics , bacteria , escherichia coli , microbiology and biotechnology , population , persistence (discontinuity) , veterinary medicine , cephalosporin , antibiotic resistance , zoology , medicine , biochemistry , geotechnical engineering , environmental health , gene , genetics , engineering
Summary 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 E scherichia 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 e GFP ‐labelled E . coli were present in the bedding (∼ 2 log g −1 ) resulting in amplification of the e GFP E . coli population ∼ 2.1 log more than e GFP 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 ID 50 (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.