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The mef(E)-carrying genetic element (mega) of Streptococcus pneumoniae: insertion sites and association with other

Maria Del Grosso1, Romina Camilli, Francesco Iannelli

  • 1Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy.

Antimicrobial Agents and Chemotherapy
|September 29, 2006
PubMed

Insights

The macrolide efflux genetic assembly (mega) element in Streptococcus pneumoniae frequently integrates into specific genomic sites. This element, encoding an efflux system, often co-localizes with other antibiotic resistance genes, contributing to multidrug resistance.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Antibiotic resistance in Streptococcus pneumoniae is a growing public health concern.
  • The macrolide efflux genetic assembly (mega) element is a mobile genetic element associated with macrolide resistance.
  • Understanding the genomic context and associations of the mega element is crucial for tracking resistance dissemination.

Purpose of the Study:

  • To investigate the structure, genomic locations, and associations of the mega element in Streptococcus pneumoniae.
  • To identify the genetic contexts in which the mega element integrates, particularly in relation to other antibiotic resistance genes.

Main Methods:

  • Analysis of 16 Streptococcus pneumoniae isolates carrying the mef(E) gene.
  • Characterization of the mega element's structure and size.
  • Identification of integration sites within the bacterial genome.
  • Investigation of co-localization with tetracycline (tet(M)) and erythromycin (erm(B)) resistance genes.

Main Results:

  • All 16 isolates possessed a similar mega element containing the mef(E)-msr(D) operon.
  • Six different integration sites for the mega element were identified in tetracycline-susceptible isolates, with five within open reading frames.
  • In isolates with tet(M), the mega element was found in various genetic contexts, including within Tn2009 and a novel composite transposon Tn2010 (mega-erm(B)).
  • The mega element was not physically linked to tet(M) in three isolates, where tet(M) was associated with erm(B) in Tn3872.
  • Tn2009 and Tn2010 were not transferable by conjugation.

Conclusions:

  • The mega element is a conserved genetic assembly in Streptococcus pneumoniae.
  • Preferential integration sites exist for composite Tn916-like elements carrying multiple resistance determinants in S. pneumoniae.
  • The co-localization of mega with tet(M) and erm(B) in novel composite transposons highlights mechanisms for the spread of multidrug resistance.

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