title: Structure and dissemination of a chromosomal insertion element encoding macrolide efflux in Streptococcus pneumoniae.
abstract: Macrolide resistance associated with macrolide efflux (mef) has rapidly increased in Streptococcus pneumoniae. We defined the genetic structure and dissemination of a novel mefE-containing chromosomal insertion element. The mefE gene was found on the 5' end of a 5.5- or 5.4-kb insertion designated as the macrolide efflux genetic assembly (mega), which is found in > or =4 distinct sites of the pneumococcal genome. The element was transformable and conferred macrolide resistance to susceptible S. pneumoniae. The first 2 open-reading frames (ORFs) of the element formed an operon composed of mefE and a predicted adenosine triphosphate-binding cassette homologous to msrA. Convergent to this efflux operon were 3 ORFs with homology to stress response genes of Tn5252. Mega was related to the recently described mefA-containing element Tn1207.1 but lacked the genes necessary for transposition and had unique termini and insertion sites. In metropolitan Atlanta, macrolide resistance due to mega rapidly increased in S. pneumoniae by clonal expansion and horizontally by transformation.
authors.affiliation: Departments of Medicine and of Microbiology and Immunology, Emory University School of Medicine, and Department of Veterans Affairs Medical Center, Atlanta, Georgia, USA. kkg6@cdc.gov
authors.forename: K
authors.initials: K
authors.lastname: Gay
authors.forename: D S
authors.initials: DS
authors.lastname: Stephens
mesh_terms: D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D002876:Chromosomes, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D008565:Membrane Proteins / Q000235:genetics; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D009690:Nucleic Acid Conformation; D016366:Open Reading Frames; D009876:Operon; D016415:Sequence Alignment; D013296:Streptococcus pneumoniae / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; C117866:MefA protein, Streptococcus; C431304:MefE protein, Streptococcus pneumoniae; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; C066202:msrA protein, Staphylococcus epidermidis