title: Co-transfer of vanA and aggregation substance genes from Enterococcus faecalis isolates in intra- and interspecies matings.
abstract: OBJECTIVE
  The study was undertaken to investigate vancomycin-resistant (vanA) Enterococcus faecalis isolates carrying aggregation substance (AS) gene(s) for their ability to co-transfer vanA and AS genes.
  
  
  METHODS
  Six vanA clumping-positive E. faecalis isolates (five human and one food sample) carrying one or more AS genes (prgB, asa1, asa373) were analysed for co-transfer of vanA and AS genes to E. faecalis JH2-2 and Enterococcus faecium 64/3.
  
  
  RESULTS
  E. faecalis isolates harboured one or multiple plasmids carrying vanA, one or more AS gene(s) or both. vanA was transferred to JH2-2 (frequencies of 10(-3)-10(-6)) from all donors and to 64/3 (10(- 6)-10(- 8)) only from donors from humans. AS genes were detected in 51/60 (85%) of JH2-2 and in 20/50 (40%) of 64/3 vanA transconjugants (prgB, asa1, asa373 or prgB asa373), of which a total of 53.6% were clumping-positive. The plasmid content of JH2-2 transconjugants from the same donor was either identical to that of the donor or it was completely different, suggesting different mechanisms for co-transfer (location on the same pheromone plasmid, mobilization of vanA plasmids by the pheromone-inducible conjugation system, rearrangement of plasmid content during matings). After induction with pheromones, a marked increase in adhesion to Caco-2 cells was observed in four isolates and in some JH2-2 transconjugants, all clumping-positive.
  
  
  CONCLUSIONS
  Findings suggest that co-transfer of vanA and AS genes may be a common feature of E. faecalis isolates. Since AS is recognized as a virulence factor, this feature might contribute to the emergence of strains with enhanced ability to cause infection and disease in humans.
authors.affiliation: Institute of Microbiology and Biomedical Sciences, Polytechnic University of Marche, 60100 Ancona, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Paoletti
authors.forename: Gessica
authors.initials: G
authors.lastname: Foglia
authors.forename: Maria Stella
authors.initials: MS
authors.lastname: Princivalli
authors.forename: Gloria
authors.initials: G
authors.lastname: Magi
authors.forename: Emilio
authors.initials: E
authors.lastname: Guaglianone
authors.forename: Gianfranco
authors.initials: G
authors.lastname: Donelli
authors.forename: Carla
authors.initials: C
authors.lastname: Pruzzo
authors.forename: Francesca
authors.initials: F
authors.lastname: Biavasco
authors.forename: Bruna
authors.initials: B
authors.lastname: Facinelli
mesh_terms: D001422:Bacterial Adhesion; D001426:Bacterial Proteins / Q000235:genetics*; D018938:Caco-2 Cells; D019729:Carbon-Oxygen Ligases / Q000235:genetics*; D003227:Conjugation, Genetic; D013293:Enterococcus faecalis / Q000235:genetics* / Q000302:isolation & purification / Q000502:physiology; D016984:Enterococcus faecium / Q000235:genetics; D005516:Food Microbiology; D006801:Humans; D010675:Pheromones / Q000235:genetics; D014640:Vancomycin; D020713:Vancomycin Resistance / Q000235:genetics*; D037521:Virulence Factors
chemical_list: D001426:Bacterial Proteins; D010675:Pheromones; C071437:VanA ligase, Bacteria; D037521:Virulence Factors; D014640:Vancomycin; D019729:Carbon-Oxygen Ligases