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Characterization of ermB gene transposition by Tn1545 and Tn917 in macrolide-resistant Streptococcus pneumoniae

Naohiro Okitsu1, Satoru Kaieda, Hisakazu Yano

  • 1Department of Environmental Infectious Disease, Graduate School of Medicine, Kitasato University, Sagamihara, Kanagawa 228-8555, Japan.

Journal of Clinical Microbiology
|January 7, 2005
PubMed

Insights

In Japanese Streptococcus pneumoniae, the ermB gene confers macrolide resistance. Transposon Tn917 primarily carries and spreads this gene, unlike Tn1545, impacting antibiotic resistance patterns.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • The ermB gene in Streptococcus pneumoniae confers resistance to macrolide antibiotics.
  • This gene is frequently located on mobile genetic elements like transposons Tn917 and Tn1545.
  • Understanding the carriage and spread of ermB is crucial for managing macrolide resistance.

Purpose of the Study:

  • To investigate the association between macrolide resistance and the ermB gene carried by Tn917 or Tn1545 in Japanese pneumococcal isolates.
  • To characterize the genetic features and spread mechanisms of these transposons in relation to antibiotic resistance.

Main Methods:

  • Analysis of 84 Japanese Streptococcus pneumoniae isolates for macrolide resistance.
  • Classification of resistant strains based on antibiotic susceptibility profiles (erythromycin, rokitamycin) and ermB gene location (Tn917, Tn1545).
  • Investigation of genetic alterations in the ermB promoter region and leader peptide.
  • Pulsed-field gel electrophoresis and serogrouping to determine transposon spread patterns.

Main Results:

  • Two groups of macrolide-resistant strains were identified: Group 1 (ermB on Tn1545) with high erythromycin resistance but susceptibility to rokitamycin, and Group 2 (ermB on Tn917) with high resistance to both.
  • Group 2 strains exhibited promoter deletions and TAAA motif insertions in the ermB leader peptide.
  • Pulsed-field gel electrophoresis indicated Tn1545 spread clonally, whereas Tn917 spread both horizontally and clonally.
  • The ermB gene was primarily carried and spread by Tn917 in the studied Japanese isolates.

Conclusions:

  • Transposon Tn917 is the predominant carrier and spreader of the ermB gene in macrolide-resistant Streptococcus pneumoniae isolates in Japan.
  • Distinct genetic features and spread mechanisms of Tn917 and Tn1545 contribute to varying macrolide resistance phenotypes.
  • The findings highlight the significant role of Tn917 in the dissemination of macrolide resistance in pneumococci.

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