Demonstration of in vivo transfer of doxycycline resistance mediated by a novel transposon

J Antimicrob Chemother. 2007 Nov;60(5):973-80. doi: 10.1093/jac/dkm331. Epub 2007 Sep 13.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism
  • Conjugation, Genetic
  • DNA Transposable Elements / genetics*
  • DNA, Bacterial / genetics
  • Doxycycline / pharmacology*
  • Drug Resistance, Bacterial / genetics*
  • Erythromycin / pharmacology
  • Gene Expression Regulation, Bacterial
  • Humans
  • Periodontal Diseases / microbiology
  • Phylogeny
  • Streptococcal Infections / microbiology
  • Streptococcus / drug effects*
  • Streptococcus / genetics*


  • Anti-Bacterial Agents
  • Bacterial Proteins
  • DNA Transposable Elements
  • DNA, Bacterial
  • Erythromycin
  • Doxycycline