title: Analysis of tetracycline resistance tet(W) genes and their flanking sequences in intestinal Bifidobacterium species.
abstract: OBJECTIVE
  The tet(W) gene provides tetracycline resistance to a wide range of anaerobic intestinal and ruminal bacteria, but little is known about the molecular organization of the tet(W) gene. The aim of this study was to gain new insights into the molecular organization of the tet(W) gene in bifidobacteria strains from humans.
  
  
  METHODS
  A segment of DNA encompassing the whole tet(W) gene and its immediate upstream and downstream sequences was analysed in 10 representative strains of four Bifidobacterium species, of which two have been shown to be tetracycline-susceptible. The non-conserved flanking regions of the tet(W) gene were further analysed in six strains.
  
  
  RESULTS
  All 10 strains share a core DNA domain of 2154 bp [starting 250 bp upstream of the tet(W) gene start codon and ending 13 bp before the stop codon] with 98% to 100% DNA identity. Except for Bifidobacterium animalis E43, all other strains further share 408 bp upstream and 70 bp downstream of the tet(W) gene. An insertion-like element of 736 bp was found to interrupt the tet(W) coding sequence in Bifidobacterium longum M21, which may be the reason for its tetracycline susceptibility. However, genetic events explaining the susceptible phenotype of B. longum LMG 13197(T) were not observed.
  
  
  CONCLUSIONS
  The tet(W) genes from all 10 strains shared 98% to 100% DNA and amino acid identity, though large variation was found in their flanking regions.
authors.affiliation: Departamento de Microbiología y Bioquímica, Instituto de Productos Lácteos de Asturias (CSIC), Carretera de Infiesto s/n, 33300 Villaviciosa, Asturias, Spain.
authors.forename: Mohammed Salim
authors.initials: MS
authors.lastname: Ammor
authors.forename: Ana Belén
authors.initials: AB
authors.lastname: Flórez
authors.forename: Pablo
authors.initials: P
authors.lastname: Alvarez-Martín
authors.forename: Abelardo
authors.initials: A
authors.lastname: Margolles
authors.forename: Baltasar
authors.initials: B
authors.lastname: Mayo
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics*; D001644:Bifidobacterium / Q000235:genetics* / Q000302:isolation & purification; D004251:DNA Transposable Elements; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics*; D041981:Gastrointestinal Tract / Q000382:microbiology; D006801:Humans; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D011995:Recombination, Genetic; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D013752:Tetracycline / Q000494:pharmacology; D013753:Tetracycline Resistance
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D004251:DNA Transposable Elements; D004269:DNA, Bacterial; D013752:Tetracycline