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Tn5253 family integrative and conjugative elements carrying mef(I) and catQ determinants in Streptococcus pneumoniae

Marina Mingoia1, Eleonora Morici1, Gianluca Morroni1

  • 1Unit of Microbiology, Department of Biomedical Sciences and Public Health, Polytechnic University of Marche Medical School, Ancona, Italy.

Antimicrobial Agents and Chemotherapy
|July 30, 2014
PubMed

Insights

The macrolide efflux gene mef(I) and chloramphenicol inactivation gene catQ are linked in IQ elements within Streptococcus bacteria. These elements are mobile genetic elements called integrative and conjugative elements (ICEs) that can transfer antibiotic resistance genes between bacteria.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • The macrolide efflux gene mef(I) and chloramphenicol inactivation gene catQ were first identified together in Streptococcus pneumoniae.
  • These linked genes form a module known as the IQ element, which has also been found in Streptococcus pyogenes.

Purpose of the Study:

  • To characterize the genetic elements carrying the IQ elements in Streptococcus pneumoniae and Streptococcus pyogenes.
  • To investigate the structure, integration, and transfer mechanisms of these mobile genetic elements.

Main Methods:

  • Characterization of genetic elements using PCR mapping, partial sequencing, and restriction analysis.
  • Sequencing of the integrative and conjugative element (ICE) from S. pneumoniae (ICESpn529IQ).
  • Analysis of insertion sites and integrase genes involved in chromosomal integration.

Main Results:

  • All three IQ elements studied were found to be part of Tn5253 family integrative and conjugative elements (ICEs).
  • Differences were observed in the integrase genes and associated fragments among the ICEs, with ICESpn529IQ and ICESpy029IQ sharing common features, while ICESpy005IQ differed.
  • All three ICEs lacked the typical linearized pC194 plasmid and contained a single copy of a toxin-antitoxin operon.
  • Chromosomal integration was site-specific, dependent on the integrase.
  • Only ICESpy005IQ was capable of excision and transfer by conjugation.
  • Transformation experiments showed high-frequency cotransfer of mef(I) and catQ from S. pyogenes Spy005, but low frequencies from the other strains.

Conclusions:

  • The IQ elements are integrated into Tn5253-like ICEs in both S. pneumoniae and S. pyogenes.
  • The genetic makeup and transfer capabilities of these ICEs vary, influencing the spread of antibiotic resistance genes.
  • The study highlights the role of ICEs in the dissemination of macrolide and chloramphenicol resistance genes in streptococci.

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