Selection and transfer of an IncI1-tet(A) plasmid of Escherichia coli in an ex vivo model of the porcine caecum at doxycycline concentrations caused by crosscontaminated feed

L E J Peeters, T De Mulder, E Van Coillie, J Huygens, A Smet, E Daeseleire, J Dewulf, H Imberechts, P Butaye, F Haesebrouck, S Croubels, M Heyndrickx, G Rasschaert

    Research output: Contribution to journalA1: Web of Science-articlepeer-review

    Abstract

    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 Escherichia coli and its resistance plasmid in an ex vivo model of the porcine caecum.

    METHODS AND RESULTS: A DOX-resistant, tet(A)-carrying, porcine commensal E. coli strain (EC 682) was cultivated for 6 days in the porcine caecum 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 caecum model.

    SIGNIFICANCE AND IMPACT OF THE 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.

    Original languageEnglish
    JournalJournal of Applied Microbiology
    Volume123
    Issue number5
    Pages (from-to)1312-1320
    Number of pages9
    ISSN1364-5072
    DOIs
    Publication statusPublished - Nov-2017

    Keywords

    • Journal Article

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