Co-transfer of vanA and aggregation substance genes from Enterococcus faecalis isolates in intra- and interspecies matings.
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.
Paoletti
Claudia
C
Institute of Microbiology and Biomedical Sciences, Polytechnic University of Marche, 60100 Ancona, Italy.
Foglia
Gessica
G
Princivalli
Maria Stella
MS
Magi
Gloria
G
Guaglianone
Emilio
E
Donelli
Gianfranco
G
Pruzzo
Carla
C
Biavasco
Francesca
F
Facinelli
Bruna
B
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
D001426:Bacterial Proteins; D010675:Pheromones; C071437:VanA ligase, Bacteria; D037521:Virulence Factors; D014640:Vancomycin; D019729:Carbon-Oxygen Ligases