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Characterisation of the Actinobacillus pleuropneumoniae SXT-related Integrative and Conjugative Element ICEApl2, and analysis of the encoded FloR protein: hydrophobic residues in transmembrane domains contribute dynamically to florfenicol and chloramphenicol efflux

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Title: Characterisation of the Actinobacillus pleuropneumoniae SXT-related Integrative and Conjugative Element ICEApl2, and analysis of the encoded FloR protein: hydrophobic residues in transmembrane domains contribute dynamically to florfenicol and chloramphenicol efflux
Authors: Li, Y
Li, Y
Fernandez Crespo, R
Leanse, LG
Langford, PR
Bosse, JT
Item Type: Journal Article
Abstract: Objectives To characterize ICEApl2, an SXT-related integrative and conjugative element (ICE) found in a clinical isolate of the porcine pathogen Actinobacillus pleuropneumoniae, and analyse the functional nature of the encoded FloR. Methods ICEApl2 was identified in the genome of A. pleuropneumoniae MIDG3553. Functional analysis was done using conjugal transfer experiments. MIDG3553 was tested for susceptibility to the antimicrobials for which resistance genes are present in ICEApl2. Lack of florfenicol/chloramphenicol resistance conferred by the encoded FloR protein was investigated by cloning and site-directed mutagenesis experiments in Escherichia coli. Results ICEApl2 is 92 660 bp and contains 89 genes. Comparative sequence analysis indicated that ICEApl2 is a member of the SXT/R391 ICE family. Conjugation experiments showed that, although ICEApl2 is capable of excision from the chromosome, it is not self-transmissible. ICEApl2 encodes the antimicrobial resistance genes floR, strAB, sul2 and dfrA1, and MIDG3553 is resistant to streptomycin, sulfisoxazole and trimethoprim, but not florfenicol or chloramphenicol. Cloning and site-directed mutagenesis of the floR gene revealed the importance of the nature of the hydrophobic amino acid residues at positions 160 and 228 in FloR for determining resistance to florfenicol and chloramphenicol. Conclusions Our results indicate that the nature of hydrophobic residues at positions 160 and 228 of FloR contribute dynamically to specific efflux of florfenicol and chloramphenicol, although some differences in resistance levels may depend on the bacterial host species. This is also, to our knowledge, the first description of an SXT/R391 ICE in A. pleuropneumoniae or any member of the Pasteurellaceae.
Issue Date: 6-Oct-2017
Date of Acceptance: 23-Aug-2017
URI: http://hdl.handle.net/10044/1/50488
DOI: https://dx.doi.org/10.1093/jac/dkx342
ISSN: 0305-7453
Publisher: Oxford University Press (OUP)
Start Page: 57
End Page: 65
Journal / Book Title: Journal of Antimicrobial Chemotherapy
Volume: 73
Issue: 1
Copyright Statement: © The Author 2017. Published by Oxford University Press on behalf of the British Society for Antimicrobial Chemotherapy. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited.
Sponsor/Funder: Biotechnology and Biological Sciences Research Council (BBSRC)
Biotechnology and Biological Sciences Research Council (BBSRC)
Funder's Grant Number: BB/G018553/1
BB/M023052/1
Keywords: 1115 Pharmacology And Pharmaceutical Sciences
0605 Microbiology
1108 Medical Microbiology
Microbiology
Publication Status: Published
Appears in Collections:Department of Medicine
Faculty of Medicine



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