Journal Article

Deletion of pT181-like sequence in an <i>smr</i>-encoding mosaic plasmid harboured by a persistent bovine <i>Staphylococcus warneri</i> strain

Jostein Bjorland, Terje Steinum, Marianne Sunde, Steinar Waage, Ståle Sviland, Hanne Oppegaard and Even Heir

in Journal of Antimicrobial Chemotherapy

Published on behalf of British Society for Antimicrobial Chemotherapy

Volume 57, issue 1, pages 46-51
Published in print January 2006 | ISSN: 0305-7453
Published online November 2005 | e-ISSN: 1460-2091 | DOI: http://dx.doi.org/10.1093/jac/dki407
Deletion of pT181-like sequence in an smr-encoding mosaic plasmid harboured by a persistent bovine Staphylococcus warneri strain

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Objectives: The aim was to study the persistence and characteristics of Staphylococcus warneri strains resistant to quaternary ammonium compounds (QACs), including sequencing and analysis of two plasmids proved to carry the smr gene.

Methods: During a 3.5 year period quarter milk samples were collected on three occasions from all lactating cows in a dairy herd. The samples were screened with regard to QAC-resistant bacteria using a selective medium. Thirty randomly selected QAC-resistant S. warneri were typed by PFGE and subjected to plasmid isolation and analysis followed by gene detection using PCR. Two smr-containing plasmids in S. warneri isolates were sequenced.

Results: All isolates from the initial collection of quarter milk contained smr residing on a 5.8 kb plasmid (pSW174), which contained regions with high similarities to various plasmids, including pT181, pSK108 and pPI-2. The pT181-like sequence was flanked by 148 bp direct repeats, denoted ISLE49, with high similarity to previously reported sequences of ∼148 bp, including ISLE39 flanking the insertion sequence IS257 in methicillin-resistant Staphylococcus aureus. All isolates from subsequent collections of quarter milk harboured a smaller smr-containing plasmid (pSW49). Sequence analyses revealed pSW49 (3552 bp) to be an in-part deleted version of pSW174 (5767 bp).

Conclusions: The IS-associated elements found in this study may have a wider role in the integration and excision of DNA sequences in staphylococci than previously reported. The mosaic plasmid structure based on genetic elements of various origins contributes to further knowledge on the flexibility of smr-encoding plasmids.

Keywords: Staphylococcus; resistance; quaternary ammonium compounds; tetracycline

Journal Article.  4251 words.  Illustrated.

Subjects: Medical Oncology ; Critical Care

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