RESUMEN
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.
Asunto(s)
Proteínas Bacterianas/genética , Ligasas de Carbono-Oxígeno/genética , Enterococcus/genética , Transferencia de Gen Horizontal , Staphylococcus aureus/genética , Proteínas Bacterianas/metabolismo , Ligasas de Carbono-Oxígeno/metabolismo , Conjugación Genética , Enterococcus/efectos de los fármacos , Enterococcus/enzimología , Infecciones por Bacterias Grampositivas/microbiología , Humanos , Pruebas de Sensibilidad Microbiana , Infecciones Estafilocócicas/microbiología , Staphylococcus aureus/efectos de los fármacos , Vancomicina/farmacología , Resistencia a la VancomicinaRESUMEN
In this study, Enterocin 416K1, a bacteriocin produced by Enterococcus casseliflavus IM 416K1, was entrapped in an organic-inorganic hybrid coating applied to a LDPE (low-density polyethylene) film for its potential use in the active food packaging field. The antibacterial activity of the coated film was evaluated against Listeria monocytogenes NCTC 10888 by qualitative modified agar diffusion assay, quantitative determination in listeria saline solution suspension and direct contact with artificially contaminated food samples (frankfurters and fresh cheeses) stored at room and refrigeration temperatures. All investigations demonstrated that enterocin-activated coatings have a good anti-listeria activity. Qualitative tests showed a clear zone of inhibition in the indicator lawn in contact with and around the coated film. During the quantitative antibacterial evaluation the L. monocytogenes viable counts decreased to 1.5 log units compared to the control. The inhibitory capability was confirmed also in food-contact assays. In all food samples packed with coated films we observed a significant decrease in L. monocytogenes viable counts in the first 24 h compared to the control. This difference was generally maintained up to the seventh day and then decreased, with the exception of the cheese samples stored at refrigeration temperature.
Asunto(s)
Antibacterianos/farmacología , Queso/microbiología , Enterococcus/metabolismo , Embalaje de Alimentos/métodos , Listeria monocytogenes/efectos de los fármacos , Hidrocarburos Aromáticos con Puentes/farmacología , Recuento de Colonia Microbiana , Seguridad de Productos para el Consumidor , Contaminación de Alimentos/prevención & control , Microbiología de Alimentos , Conservación de Alimentos/métodos , Humanos , Listeria monocytogenes/crecimiento & desarrollo , Factores de TiempoRESUMEN
Vancomycin-resistant enterococci (VRE) in healthy people and in food-producing animals seems to be quite common in Europe. The existence of this community reservoir of VRE has been associated with the massive use of avoparcin in animal husbandry. Eight years after the avoparcin ban in Europe, we investigated the incidence of VanA enterococci, their resistance patterns, and the mobility of their glycopeptide-resistance determinants in a sampling of animal rectal swabs and clinical specimens. A total of 259 enterococci isolated from equine, swine, and clinical samples were subcultured on KF-streptococcus agar (Difco Laboratories, Detroit, MI) supplemented with vancomycin and teicoplanin; 7 (6.7%), 10 (16%), and 8 (8.6%) respectively were found to be glycopeptides resistant (VanA phenotype). Slight differences in antimicrobial resistance patterns resulted among VRE recovered from the different sources. Polymerase chain reaction amplification demonstrated the presence of the vanA gene cluster and its extrachromosomal location in VRE plasmid DNA. VanA resistance was transferred in 7 out of 25 mating experiments, 4 with clinical, 2 with swine, and only 1 with equine donors. The conjugative plasmids of animal strains showed a high homology in the restriction profiles, unlike plasmids of clinical microrganisms. Our observations confirmed the possible horizontal transfer of VanA plasmids across different strains and, consequently, the diffusion of the vancomycin-resistance determinants.
Asunto(s)
Proteínas Bacterianas/genética , Ligasas de Carbono-Oxígeno/genética , Enterococcus/efectos de los fármacos , Infecciones por Bacterias Grampositivas/microbiología , Infecciones por Bacterias Grampositivas/veterinaria , Enfermedades de los Caballos/microbiología , Recto/microbiología , Enfermedades de los Porcinos/microbiología , Resistencia a la Vancomicina/genética , Animales , Enterococcus/genética , Enterococcus/aislamiento & purificación , Transferencia de Gen Horizontal , Caballos , Humanos , Porcinos , Orina/microbiología , Heridas y Lesiones/microbiologíaRESUMEN
Five penicillinase producing Neisseria gonorrhoeae (PPNG) were isolated from urethral specimens of men admitted to the "Santa Chiara" Hospital (Trento, Italy). All strains proved to be resistant to penicillin and ampicillin, and sensitive to cefuroxime, erythromycin, tetracycline, spectinomycin, nalidixic acid and ciprofloxacin. PPNG plasmid profiles showed that four of the isolates carried the 3.2 MDa "Africa" plasmid and one the 4.5 MDa "Asia" plasmid, the two well-known phenotypes reported in the USA and Europe as well as in Asian and African countries. Membrane matings were performed using N. gonorrhoeae carrying the 24.5 MDa conjugative plasmid as donors and E. coli K12 J 53 as recipient. The transfer of beta-lactamic antibiotic resistance was supported by the presence of 4.5 or 3.2 MDa plasmid bands and by beta-lactamase production in the transconjugants. Restriction analysis of Asian and African plasmids is reported.