title: Vancomycin-resistance transferability from VanA enterococci to Staphylococcus aureus.
abstract: In last decade methicillin-resistant Staphylococcus aureus with high level of vancomycin-resistance (VRSA) have been reported and generally the patients with VRSA infection were also infected with a vancomycin-resistant Enterococcus (VRE). Considering that the high level of vancomycin-resistance in VRSA isolates seems to involve the horizontal transfer of Tn1546 transposon containing vanA gene from coinfecting VRE strains, the authors have studied the "in vitro" conjugative transfer of this resistance from VanA enterococci to S. aureus. Out of 25 matings performed combining five vancomycin-resistant enterococci as donors (three Enterococcus faecalis and two Enterococcus faecium), and five S. aureus as recipients, all clinical isolates, two have been successful using E. faecalis as donor. The transfer of vancomycin-resistance was confirmed by vanA gene amplification in both transconjugants and the resistance was expressed at lower levels (MIC 32 μg/ml) in comparison with the respective VRE donors (MIC > 128 μg/ml). The vancomycin-resistance of trasconjugants was maintained even after subsequent overnight passages on MSA plates containing subinhibitory levels of vancomycin. This study shows that the vanA gene transfer can be achieved through techniques "in vitro" without the use of laboratory animals employed, in the only similar experiment previously carried out by other authors, as substrate for the trasconjugant growth. Moreover, in that previous experiment, contrary to this study, the vancomycin resistant S. aureus trasconjugants were selected on erythromycin agar and not by direct vancomycin agar selection.
authors.affiliation: Department of Biomedical Sciences, University of Modena and Reggio Emilia, Via Campi 287, 41125 Modena, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: de Niederhäusern
authors.forename: Moreno
authors.initials: M
authors.lastname: Bondi
authors.forename: Patrizia
authors.initials: P
authors.lastname: Messi
authors.forename: Ramona
authors.initials: R
authors.lastname: Iseppi
authors.forename: Carla
authors.initials: C
authors.lastname: Sabia
authors.forename: Giuliano
authors.initials: G
authors.lastname: Manicardi
authors.forename: Immacolata
authors.initials: I
authors.lastname: Anacarso
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D019729:Carbon-Oxygen Ligases / Q000235:genetics* / Q000378:metabolism; D003227:Conjugation, Genetic; D016983:Enterococcus / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D022761:Gene Transfer, Horizontal; D016908:Gram-Positive Bacterial Infections / Q000382:microbiology; D006801:Humans; D008826:Microbial Sensitivity Tests; D013203:Staphylococcal Infections / Q000382:microbiology; D013211:Staphylococcus aureus / Q000187:drug effects / Q000235:genetics*; D014640:Vancomycin / Q000494:pharmacology; D020713:Vancomycin Resistance
chemical_list: D001426:Bacterial Proteins; C071437:VanA ligase, Bacteria; D014640:Vancomycin; D019729:Carbon-Oxygen Ligases