Journal Article

Molecular analysis of florfenicol-resistant <i>Escherichia coli</i> isolates from pigs

Maren Blickwede and Stefan Schwarz

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 53, issue 1, pages 58-64
Published in print January 2004 | ISSN: 0305-7453
Published online January 2004 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dkh007
Molecular analysis of florfenicol-resistant Escherichia coli  isolates from pigs

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Objectives: The aim of this study was to analyse florfenicol-resistant Escherichia coli isolates from pigs for the genetic basis of florfenicol resistance, and to compare these data with those previously determined for E. coli isolates from cattle and poultry.

Methods: Fourteen porcine E. coli isolates were included in this study and subjected to serotyping, plasmid profiling and macrorestriction analysis. MICs of florfenicol were determined by broth microdilution. The presence of the gene floR was confirmed by hybridization and PCR analysis. Transformation experiments were conducted to isolate florfenicol resistance plasmids. The floR region of a florfenicol resistance plasmid was cloned and sequenced.

Results: All florfenicol-resistant E. coli isolates exhibited MICs of florfenicol >128 mg/L and carried the floR gene. A single isolate had a floR-carrying plasmid of ∼35 kb, designated pMBSF1. Sequence analysis identified the floR gene flanked by truncated transposase genes. Moreover, a truncated copy of Tn5393 with complete streptomycin resistance genes strA and strB was found upstream of the floR gene of pMBSF1. Chromosomally resistant E. coli isolates, which shared the same BlnI macrorestriction pattern, differed in their floR hybridization patterns.

Conclusion: The plasmid pMBSF1 is the smallest floR-carrying plasmid reported to date. Its floR region differed from those previously found in E. coli isolates from cattle. Variations in the RFLPs of chromosomal EcoRI fragments carrying floR in isolates that had the same macrorestriction pattern might suggest variable chromosomal integration sites.

Keywords: Keywords: florfenicol resistance, floR gene, transposon Tn5393, transposon Tn1721, recombination

Journal Article.  4488 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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