title: Genetic elements carrying macrolide efflux genes in streptococci.
abstract: Type M resistance to macrolides in Streptococcus pyogenes and Streptococcus pneumoniae is associated to the presence of macrolide efflux genes (mef). These genes are carried by 3 very conserved chromosomal genetic elements: (i) "mega", 5.5 kb, typical of S. pneumoniae, carries mef(E), can insert at different sites in the bacterial chromosome and in other genetic elements, does not have genes encoding putative recombinases or transposases, and it is not conjugative; (ii) Tn1207.3, 54, 52 kb, typical of S. pyogenes, carries mef(A), it integrates at a single specific site in the bacterial chromosome, carries 3 ORFs encoding for putative recombinases, it is transferred by conjugation among different streptococcal species, and its genome resembles that of a bacteriophage; (iii) Tn1207.1, 7.2 kb, is a defective form of Tn1207.3 found in a clonal population of S. pneumoniae, it carries mef(A), it integrates at a single specific site in the bacterial chromosome (the same of Tn1207.3), and it is not conjugative.
authors.affiliation: Laboratory of Molecular Microbiology and Biotechnology (LAMMB), Department of Molecular Biology, Univeresity of Siena, 53100 Siena, Italy. pozzi@unisi.it
authors.forename: Gianni
authors.initials: G
authors.lastname: Pozzi
authors.forename: Francesco
authors.initials: F
authors.lastname: Iannelli
authors.forename: Marco R
authors.initials: MR
authors.lastname: Oggioni
authors.forename: Maria
authors.initials: M
authors.lastname: Santagati
authors.forename: Stefania
authors.initials: S
authors.lastname: Stefani
mesh_terms: D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000494:pharmacology*; D001435:Bacteriophages / Q000235:genetics / Q000502:physiology; D004251:DNA Transposable Elements / Q000235:genetics; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D005798:Genes, Bacterial / Q000235:genetics*; D018942:Macrolides / Q000378:metabolism* / Q000494:pharmacology*; D013291:Streptococcus / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D004251:DNA Transposable Elements; D018942:Macrolides