Molecular mechanisms of high level tetracycline-resistance in group A streptococcal isolates, T serotypes 4 and 11

Int J Antimicrob Agents. 2005 Feb;25(2):142-7. doi: 10.1016/j.ijantimicag.2004.09.014.


The molecular mechanism of high level tetracycline resistance in T serotypes 4 and 11 group A streptococcal (GAS) isolates was examined in 61 tetracycline-resistant isolates in Japan. PCR and sequencing analyses revealed that the T serotype/emm genotype, T4/4 isolates carried tet(O) genes, which were genetically homogenous. The T11/11 and T11/89 isolates carried different subtypes of tet(M) genes, which were present on transposons Tn916 and Tn1545, respectively. In addition, these T11 isolates may have obtained the tet(M) gene after the 1990s, because resistance to tetracycline in T11 isolates was rarely found before then. These results strongly suggested that the T4 and T11 GAS isolates acquired tetracycline-resistance via different molecular mechanisms.

MeSH terms

  • Bacterial Proteins / genetics*
  • Carrier Proteins / genetics*
  • DNA Transposable Elements
  • Electrophoresis, Gel, Pulsed-Field
  • Genotype
  • Humans
  • Polymerase Chain Reaction
  • Polymorphism, Restriction Fragment Length
  • Sequence Analysis, DNA
  • Serotyping
  • Streptococcus pyogenes / classification
  • Streptococcus pyogenes / drug effects*
  • Streptococcus pyogenes / genetics
  • Streptococcus pyogenes / isolation & purification
  • Tetracycline Resistance / genetics*


  • Bacterial Proteins
  • Carrier Proteins
  • DNA Transposable Elements
  • Tet M resistance protein, Bacteria
  • Tet O resistance protein, Bacteria