title: Macrolide resistance gene erm(TR) and erm(TR)-carrying genetic elements in Streptococcus agalactiae: characterization of ICESagTR7, a new composite element containing IMESp2907.
abstract: OBJECTIVE
  The objective of this study was to investigate macrolide-resistant Streptococcus agalactiae isolates harbouring erm(TR), an erm(A) gene subclass, with emphasis on their erm(TR)-carrying genetic elements. Four erm(TR)-carrying elements have been described to date: three closely related (ICE10750-RD.2, Tn1806 and ICESp1108) in Streptococcus pyogenes, Streptococcus pneumoniae and S. pyogenes, respectively; and one completely different (IMESp2907, embedded in ICESp2906 to form ICESp2905) in S. pyogenes.
  
  
  METHODS
  Seventeen macrolide-resistant erm(TR)-positive S. agalactiae isolates were phenotypically and genotypically characterized. Their erm(TR)-carrying elements were explored by analysing the distinctive recombination genes of known erm(TR)-carrying integrative and conjugative elements (ICEs) and by PCR mapping. The new genetic context and organization of IMESp2907 in S. agalactiae were explored using several experimental procedures and in silico analyses.
  
  
  RESULTS
  Five isolates harboured ICE10750-RD.2/Tn1806, five isolates harboured ICESp1108 and five isolates bore unknown erm(TR)-carrying elements. The remaining two isolates, exhibiting identical serotypes and pulsotypes, harboured IMESp2907 in a new genetic environment, which was further investigated in one of the two isolates, SagTR7. IMESp2907 was circularizable in S. agalactiae, as described in S. pyogenes. The new IMESp2907 junctions were identified based on its site-specific integration; the att sites were almost identical to those in S. pyogenes. In strain SagTR7, erm(TR)-carrying IMESp2907 was embedded in an erm(TR)-less internal element related to ICE10750-RD.2/Tn1806, which, in turn, was embedded in an ICESde3396-like element. The resulting whole ICE, ICESagTR7 (∼129 kb), was integrated into the chromosome downstream of the rplL gene, and was excisable in circular form and transferable by conjugation.
  
  
  CONCLUSIONS
  This is the first study exploring erm(TR)-carrying genetic elements in S. agalactiae.
authors.affiliation: Unit of Microbiology, Department of Biomedical Sciences and Public Health, Polytechnic University of Marche, Ancona, Italy m.mingoia@univpm.it.
authors.forename: Marina
authors.initials: M
authors.lastname: Mingoia
authors.affiliation: Unit of Microbiology, Department of Biomedical Sciences and Public Health, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Morici
authors.affiliation: Unit of Microbiology, Department of Biomedical Sciences and Public Health, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Emanuela
authors.initials: E
authors.lastname: Marini
authors.affiliation: Unit of Microbiology, Department of Biomedical Sciences and Public Health, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Brenciani
authors.affiliation: Unit of Microbiology, Department of Life and Environmental Sciences, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Eleonora
authors.initials: E
authors.lastname: Giovanetti
authors.affiliation: Unit of Microbiology, Department of Biomedical Sciences and Public Health, Polytechnic University of Marche, Ancona, Italy.
authors.forename: Pietro E
authors.initials: PE
authors.lastname: Varaldo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D006801:Humans; D020071:Interspersed Repetitive Sequences; D018942:Macrolides / Q000494:pharmacology*; D008780:Methyltransferases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D013290:Streptococcal Infections / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D004269:DNA, Bacterial; D018942:Macrolides; D008780:Methyltransferases; C035181:rRNA (adenosine-O-2'-)methyltransferase