Detection Of The Vancomycin-resistant Genotype In Enterococci And Study Of Its Molecular Epidemiology

Along with the wide application of antimicrobial agents,enterococci have become an important source of nosocomial infection.Consequently,the resistance to vancomycin of enterococci has caused significant difficulty for clinical therapy. Moreover,it can not only resist to vancomycin itself,but possess a potent ability to transmit the resistance to others.The results of present study may contribute to reasonable selection of antimicrobial agents based on the study of molecular biological mechanism and molecular epidemiology of vancomycin-resistant enterococcus.Objectives Investigating the sensitivity of enterococcus to vancomycin and the study of drug resistance,drug resistance genotype and homology in the enterococcus with low sensitivity to glycopeptides antibiotics.Providing molecular epidemiology reference for the same drug resistant genotype and rational utility of antibiotics in clinic.Methods The sensitivity test to vancomycin was conducted in the seventy-two isolates of enterococci by agar dilution.Ten isolates with middle sensitivity to vancomycin were tested in sensitivity to 13 commonly used antibiotics.The presence of genes including Van A,Van B,Van C₁ and Van C₂ was detected with polymerase chain reaction(PCR)in the isolates with middle sensitivity to vancomycin.Taking enterobacterial repetitive integenic consensus as primer binding site,the genes were amplified for analysis of homology in the 10 isolates of enterococci with middle sensitivity to vanomycin by PCR.Results None of the isolated 10 enterococci strains was resistant to teicoplanin and linezolid,while the resistant rates to other commonly used antimicrobial agents were more than 50%.The VanC₂ gene was present in two of the 10 isolates,while the other three genes,VanA,VanB and VanC₁,were absent.The ten enterococci isolates were devided into 8 types with ERIC-PCR,in which a high homology was observed in isolates from the same hospital.Conclusions The multidrug resistant phenomenon is significant in enterococci with middle sensitivity to vancomycin.The drug resistant rate is over 50%to many commonly used antimicrobial drugs,but is sensitive to both Teicoplanin and linezolid. Therefore,teicoplanin and linezolid can be used as a first choice for infection by vancomycin.The drug resistant genotype is not VanA in the ten isolates of enterococci, in two of which the Van C₂ is positive by PCR amplification.It needs a further investigation to determine whether Van D,Van E,and Van G are present or not in other eight isolates of enterococci.Although no isolates of enterococci-resistant to vancomycin were detected,the isolates of enterococci with middle sensitivity to vanomycin were present which may be in close association with the wide application of vanomycin in clinics.The clone dissemilation between strains may exist in resistance to vanomycin of enterococci.