Journal Article

<i>tet</i>(L)-mediated tetracycline resistance in bovine <i>Mannheimia</i> and <i>Pasteurella</i> isolates

Corinna Kehrenberg, Boudewijn Catry, Freddy Haesebrouck, Aart de Kruif and Stefan Schwarz

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 56, issue 2, pages 403-406
Published in print August 2005 | ISSN: 0305-7453
Published online June 2005 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dki210
tet(L)-mediated tetracycline resistance in bovine Mannheimia  and Pasteurella isolates

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Objectives: Tetracycline-resistant Mannheimia and Pasteurella isolates, which were negative for the tetracycline resistance genes (tet) commonly detected among these bacteria, were investigated for other tet genes present and their location.

Methods: Mannheimia and Pasteurella isolates were investigated for their MICs of tetracycline and their plasmid content. Identification of tet genes was achieved by PCR. Plasmids mediating tetracycline resistance were identified by transformation and hybridization experiments. Plasmid pCCK3259 from Mannheimia haemolytica was sequenced completely and analysed for its structure and organization.

Results: All tetracycline-resistant isolates carried the gene tet(L) either on plasmids or on the chromosome. Two M. haemolytica isolates and one Mannheimia glucosida isolate harboured a common 5.3 kb tet(L) plasmid, designated pCCK3259. This plasmid was similar to the tet(B)-carrying tetracycline resistance plasmid pHS-Tet from Haemophilus parasuis and the streptomycin/spectinomycin resistance plasmid pCCK647 from Pasteurella multocida in the parts coding for mobilization functions. The tet(L) gene was closely related to that of the Geobacillus stearothermophilus plasmid pTB19. However, the translational attenuator responsible for the tetracycline-inducible expression of tet(L) was missing in plasmid pCCK3259. A recombination site was identified downstream of tet(L), which might explain the integration of the tet(L) gene region into a basic pCCK3259 replicon.

Conclusion: A tet(L) gene was shown for the first time to be responsible for tetracycline resistance in Mannheimia and Pasteurella isolates. This report demonstrates a lateral transfer of a tetracycline efflux gene in Gram-negative bovine respiratory tract pathogens, probably originating from Gram-positive bacteria.

Keywords: respiratory tract pathogens; antimicrobial resistance; gene transfer; recombination; cattle

Journal Article.  2275 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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