Vancomycin-resistant Enterococci Molecular Characterization

With the wide application of antimicrobial agents, Enterococcus spp have emerged as important nosocomial pathogens. Since their initial discovery from patients in France and the United Kingdom in 1988, the rates of VRE infection and colonisation have bean steadily rising.vancomycin-resistant enterococci (VRE) have been reported worldwide.Whereas hospital outbreakswith clonally related VRE have been reported eXtensively in the United States, the prevalence of VRE remains low in Chinese hospitals. The most commonly encountered species are Enterococcus faecalis and Enterococcus faecium and the proportion of E. faecium has increased over time. At present, VRE is considered as a major threat to public health, not only it is diffult to treat but also VRE have a potential possibility to transfer the vancomycin gene to other bactercial species,and control of its dissemination constitutes a crucial challenge. The result of the study may contribute to reasonable selection of antibiotics based on the study of molecular biological mechanism and molecular epidemiology of VRE. By using agar screening method (ADSP method) to screen the possible VRE strains,and broth dilution susceptibility test were performed to test the susceptibility to vancomycin and teicoplanin.,so that we can get the information about the drug resistant phenotype of VRE stains and rational application of antibiotics in clinic.The resistance genes and virulence genes of VRE isolates were sought by PCR and sequence methods; VRE isolates were classified by MLST technique and siX isolates of VREF which emerged in 2007 and 2008 were also analyzed by PFGE to provide molecular epidemiological information for the same drug resistant genotypeObjectives To investigate the incidence of vancomycin resistant enterococcus(VRE) in Huashan hospital of Shanghai from 2007 to 2009, and to eXamine the resistant phenotype and genotype of the VRE clones.providing valuable information about the therapy of infection in chinic.Methods A total of 890 non-repetive clinical isolates of enterococcus were screened by agar screening method (ADSP method). Broth dilution susceptibility test was performed to test the susceptibility to vancomycin and teicoplanin.13 isolates of VRE were also tested in sensitivity to 6 commonly used antibiotics.The resistance genes were sought by PCR and sequence methods.Results 13 VRE isolates were identified by using ADSP method and broth dilution susceptibility test.6 isolates of VRE (2007-2008) harbored a potentially novel vancomycin resistance gene, these 6 isolates were resistant to vancomycin but sensitive to teicoplanin (MIC of vancomycin was 32 to 256 ug/ml); The other seven isolates (2009) harbored vanA gene. The MIC of vancomycin was 32 to 64 ug/ml, the MIC of teicoplanin was 16 to 32ug/ml.None of the13 strains was resistant to linezolid,but all isolates were resistant to ampicillin,gentamicin, Ciprofloxacin, erythromycin,while some VRE strains were resistant to chloramphenicol.Conclusions The present study suggests that VRE stains identified in Huashan hospital were commonly multidrug resistant, but is sensitive to linezolid. Therefore, linezolid can be used the first choice to treat VRE infections in clinic. What's more, our research also confirmed that VREF in our hospital harbored a potentially novel vancomycin resistance gene, the further work needs to be done to investgate the function and the location of this novel gene.Objectives Applying two kinds of typing methods(PFGE typing and MLST typing)to study and compare the typing results of VRE strains to analyze the genetic relateness. The genes encoding virulence factors (esp,hyl) were analysed and the capacity for biofilm formation were investigated in all 13 VRE strains.Methods 13 VRE isolates were classified by MLST technique and six isolates of VREF which emerged in 2007 and 2008 were also analyzed by PFGE. What's more,virulence genes of VRE isolates were sought by PCR and sequence methods. And the biofilm formation was performed in 96 well polystyrene plate.Results Multilocus sequence typing (MLST) analysis of the E. faecium isolates showed that 4 isolates were ST18,6 isolates were ST78, two isolates were ST341,and only one isolate was ST203, and ST18,ST78,ST203 belonged to clonal complex CC17. The positive rate of esp gene and hyl gene were 69.2% and 30.8% respectively; The biofilm formation were not observed in all 13 strains.Conclusions Our findings indicate that nosocomial spread of VRE resulted from dissemination of Ent. faecium CC17. All 13 strains of VRE had similar antibiotic resitant pattern and had no capacity of biofilm formation.Objectives To know about the location and the function of the potential resistant gene of vancomycin.Methods Vancomycin resistance transference by conjugation was tested in all vanX isolates using a mating method.At the same time,the vanX gene was also transfered into a gram-positive bacteria saRN4220 by electroporation.By observing the change of the vancomycin resistance of the recipent cell, to analyze if the VanX gene is the resonable gene of the VRE.Conclusions our present data can't confirm the function of vanX gene in the formation of the vancomycin resistanc; By mating experiment,we assess that the resistant gene located in the plasmid of the isolates possiblely to a extent.