Title
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Selection and transfer of an IncI1-tet(A) plasmid of Escherichia coli in an ex vivo model of the porcine cecum at doxycycline concentrations caused by cross-contaminated feed
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Author
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Abstract
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Aims The aim of this study was to investigate the effect of subtherapeutic intestinal doxycycline (DOX) concentrations (4 and 1 mg l-1), caused by cross-contamination of feed, on the enrichment of a DOX resistant commensal E. coli and its resistance plasmid in an ex vivo model of the porcine cecum. Methods and Results A DOX resistant, tet(A) carrying, porcine commensal E. coli strain (EC 682) was cultivated for 6 days in the porcine cecum model under different conditions (0, 1 and 4 mg l-1 DOX). EC 682, other coliforms and anaerobic bacteria were enumerated daily. A selection of isolated DOX resistant coliforms (n=454) was characterized by rep-PCR clustering, PCR assays [Inc1 and tet(A)] and micro broth dilution susceptibility tests (Sensititre). Both 1 and 4 mg l-1 DOX enriched medium had a significantly higher selective effect on EC 682 and other resistant coliforms than medium without DOX. Transconjugants of EC 682 were isolated more frequently in the presence of 1 and 4 mg l-1 DOX compared to medium without DOX. Conclusions Subtherapeutic intestinal DOX concentrations have the potential to select for DOX resistant E.coli, and promote the selection of transconjugants in a porcine cecum model. Significance and Impact of Study Cross-contamination of feed with antimicrobials such as DOX likely promotes the spread of antimicrobial resistance. Therefore it is important to develop or fine-tune guidelines for the safe use of antimicrobials in animal feed and its storage. |
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Language
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English
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Source (journal)
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The journal of applied microbiology. - London
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Publication
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London
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2017
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ISSN
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1364-5072
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DOI
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10.1111/JAM.13561
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Volume/pages
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123
:5
(2017)
, p. 1312-1320
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ISI
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000413317600022
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Pubmed ID
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28799283
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Full text (Publisher's DOI)
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Full text (open access)
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