JAC Advance Access published online on September 13, 2007
Journal of Antimicrobial Chemotherapy, doi:10.1093/jac/dkm331
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Demonstration of in vivo transfer of doxycycline resistance mediated by a novel transposon
King's College London Dental Institute at Guy's, King's College and St Thomas' Hospitals, Infection Research Group, Guy's Campus, London SE1 9RT, UK
Received 21 March 2007; returned 10 May 2007; revised 6 August 2007; accepted 7 August 2007
* Correspondence address. Department of Microbiology, Floor 28, Guy's Tower, Guy's Campus, London SE1 9RT, UK. Tel: +44-20-7188-3872; Fax: +44-20-7188-3871; E-mail: william.wade{at}kcl.ac.uk
Objectives: The aim of this study was to investigate the transfer of bacterial doxycycline resistance between oral bacteria in subjects receiving systemic doxycycline for the treatment of periodontitis.
Patients and methods: Streptococci were cultured before and after treatment from the subgingival plaque of two patients with periodontitis, genotyped and investigated for the presence of antimicrobial resistance determinants and conjugative transposons.
Results: In one subject, a strain of Streptococcus sanguinis resistant to doxycycline was a minor component of the pre-treatment streptococcal flora but dominated post-treatment. In a second subject, a strain of Streptococcus cristatus, which was sensitive to doxycycline before treatment, was found to have acquired a novel conjugative transposon during treatment, rendering it resistant to doxycycline and erythromycin. The novel transposon, named CTn6002, was sequenced and found to be a complex element derived in part from Tn916, and an unknown element which included the erythromycin resistance gene erm(B). A strain of Streptococcus oralis isolated from this subject pre-treatment was found to harbour CTn6002 and was therefore implicated as the donor.
Conclusions: This is the first direct demonstration of transfer of antimicrobial resistance carried on a conjugative transposon between oral bacteria during systemic antimicrobial treatment of periodontitis in humans.
Key Words: transposon , tetracycline , antimicrobial resistance , periodontitis
Present address. Division of Microbial Diseases, UCL Eastman Dental Institute, London WC1X 8LD, UK.
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