The Analysis Of Drug Resistance And Research On Resistance Mechanisms Of Isolates Of Enterococcus In Ningxia

Objective To investigate the clinical distribution，specimen types and drug resistance ofEnterococcus isolated from the hospital in Ningxia. To study the drug resistance to antibioticsfrom the resistance phenotype and genotype,study the characteristics of molecularepidemiology and the resistance mechanisms,and provide a scientific basis for rational use ofantibiotics and treatment.Methods We had collected1157isolates of Enterococcus by cultured in normal methodsin General Hospital of Ningxia Medical University from January2010to December2012,andall the isolates were identified by VITEK microbe automatic system. Drug susceptibility testwas performed by the disc diffusion method (K-B) and drug resistance to16kinds ofcommonly used antibiotics were tested. The results were analyzed by the software WHONET5.6and SPSS17.0.The minimum inhibitory concentration(MIC) of vancomycin andteicoplanin for VRE were measured by E-test.582isolates of Enterococcus which aremultidrug-resistance were screened and the minimum inhibitory concentration(MIC) of threekinds of fluoroquinones(ciprofloxacin, gatifloxacin, levofloxacin) were tested by agardilution method.While the changes of the MIC of three kinds of drugs were detected afteradding reserpine. The β-lactams gene (TEM), aminoglycosides gene [aac (6’)/aph (2"), aph(3’)-Ⅲ, ant (6)-Ⅰ, ant (2")-Ⅰ, ant (4’,4")], tetracycline gene (tetM), macrolide gene(ermB, mefA), glycopeptide gene (VanA, VanB, VanC1, VanC2/3) and genes encodingefflux pumps (emeA) in Enterococci were detected by polymerase chain reaction(PCR).Glycopeptide gene products were sequenced to confirm vancomycin-resistant enterococci(VRE),and their homology were analysised by pulsed-field gel electrophoresis(PFGE). Results1157Enterococci were isolated in our hospital from January2010to December2012. Among all the strains of Enterococci there were679strains of E.faecium (58.7%),382strains of E.faecalis (33.0%),26strains of E.casseliflavus (2.2%),24strains of E.avium (2.1%)and46strains of other Entercocci(4.0%). There were363Enterococcus strains from urine(31.4%),282from liquor puris (24.4%) and185separated from secretion (16.0%). Among1157isolates, most of them were isolated from burn,ICU,paediatric,respiratory and urologydepartment. The spectrum of antibacterial agent-resistant E. faecalis was significantlydifferent from that of the E. faecium. The resistant rate to vancomycin, teicoplanin andlinezolid is lower than commonly used antibiotics,to which were more than40%.The samestrains in different departments in our hospital also showed diffetent antimicrobialresistance.The resistant rate of three fluoroquinolones were reduced in different degrees afterreserpine was used. And the total rate was was reduced from41.9%to30.1%.Among thesestrains, the rates by order of positive drug resistant genes of TEM,aac(6’)/aph(2”),aph（3’）-Ⅲ,an（t6）-Ⅰ,an（t2”）-Ⅰ,tetM, ermB and VanA were77.0%,62.4%,26.5%,12.5%,35.7%,30.8%,65.5%,0.9%. The positive rate of efflux pump genes emeA was55.0%.5VREwhich were resistant to vancomycin and teicoplanin were VanA type.And they were diviidedinto5genetic subtypes.Conclusions The infection in urinary system and respiratory system were mainly causedby E.faecalis and E.faecium with multidrug resistance and high resistance,and the rate ofresistance was rising. Reserpine could inhibit the active efflux of FQNS by the Enterococciand reduce the MIC for drug-resistant strains in vitro. Multidrug-resistant efflux pump geneemeA was relevant to antimicrobial drug resistance in enterococci. The harbored antibioticresistant genes were the very important reasons of resistance to antibiotics in enterococci.VRE in our hospital were VanA genotypes,which were divided into5genetic subtypes.Andthere was no relevance in the epidemiology. Therefore, monitoring to clinical distribution anddrug resistance of Enterococcus resistance and investigate their resistance mechanisms shows great significance to the rational use of antibiotics and prevention of nosocomial infections.