Characterization Of Virulence Determinants In Clinical Enterococcus Isolates

Objective:1.To investigate features of infections,resistance to antibiotics,as well as the distribution of 8 virulence genes(cyl A,gel E,asa1,esp,ace,acm,fsr,hyl)from clinical isolates of E.faecalis and E.faecium.The correlation between virulence genes and antibiotic resistance were discussed in order to provide treatment basis for clinical treatment.2.The prevalence of virulence genes from different samples were also investigated,for further study the pathogenesis of virulence factors.Methods:1.Totally,97 E.faecalis and E.faecium strains isolated from the first affliated hospital of CMU,the clinical information including specimen,antibiotic resistence against penicillin(PEN),ampicillin(AMP),erythromycin(ERY),levofloxacin(LVX),ciprofloxacin(CIP),high-level gentamicin(GEH),high-level streptomycin(STH),vancomycin(VAN),linezolid(LNZ),tetracycline(TCY)and teicoplanin(TEC)were collected through retrospective investigation.2.8 virulence genes(esp、cylA、hyl、gelE、asa1、fsr、ace、acm)were detected by PCR.Results were analyzed with χ2 test,a P-value of <0.05 was considered to be statistically significant,SPSS22.0 was used for statistical analysis.E.faecalis ATCC29212 was used as quality control strains.Results:1.Disribution of enterococcusAmong all 97 enterococcus strains,46 were E.faecalis,51 were E.faecium.E.faecalis strains were isolated from urine(20),blood(12),fluid(6),bile(4),pus(2),secreta(1),csf(1).E.faecium strains were from urine(18),blood(13),fluid(11),bile(6),secreta(1),csf(1),ascites(1).2.prevelance of virulence determinants in E.faecalis and E.faeciumThe detection rates of cyl A,gel E,asa1,esp,ace and fsr in E.faecalis were 63.0%,69.6%,67.4%,65.2%,28.3% and 71.7%.The detection rates of esp,acm and hyl in Enterococcus faecium were 64.7%,70.6% and 25.5%.Only one E.faecium detected cyl A,the detection rate was 2.0%.There is no gel E,fsr and asa1 positive strains.In E.faecalis,the positive rate of cyl A,gel E,asa1 and fsr was significantly higher than in E.facium(P<0.001),and the positive rate of hyl was lower than in E.facium(P<0.001).3.virulence determinants in enterococcus isolates from different specimensThe detection rates of acm and esp in 18 E.faecium isolates from urine were 88.9% and 72.2%.The virulence genes of 21 E.faecalis strains were asa1(80.0%),esp(75.0%),cyl A(70.0%),gel E(65.0%),fsr(65.0%),ace(45.0%).There were 8(61.5%)esp and acm detected in 13 blood samples of E.faecium,and 10 of 12(83.3%)E.faecalis showed asa1 positive,cyl A,gel E,esp,fsr positive were 9(75.0%).Esp was detected in 8 of 11(72.7%)E.faecium in fluid and acm was detected in 7(63.6%).In addition,csf,ascites and secreta all isolated one of E.faecium,both showed esp and acm positive.In E.faecalis,ace positive strains are almost from urine samples(69.2%,P=0.046).In E.faecium,the distribution of enterococcal virulence genes from different samples had no significant difference.4.Correlation between virulence diterminants and drug resistanceAll E.faecalis resistant to penicillin and erythromycin.The remaining resistance rate to antibiotics was ciprofloxacin(78.3%),linezolid(4.4%),vancomycin(2.2%),teicoplanin(2.2%)and tetracycline(2.2 %)Ampicillin(0%).There is a higher rates of antimicrobial resistance in E.faecium.The highest rate of resistance was erythromycin(86.3%),following by penicillin(82.4%),ciprofloxacin(80.4%),levofloxacin(78.4%),ampicillin(78.4%),high-level gentamycin(62.7%),high-level streptomycin(56.8%),tetracycline(2.0%),linezolid(0%),teicoplanin(0%).Statistical analysis show that the distribution of virulence genes is related to the antimicrobial resistance.In E.faecalis,the distribution of cyl A(P=0.001),asa1(P=0.003),esp(P<0.001)were all associated with CIP(P=0.019).In E.faecium,the distribution of esp was associated with resistance to PEN(P <0.001),AMP(P=0.001),CIP(P <0.001)and LVX(P <0.001);the distribution of acm was associated with PEN(P=0.001),AMP(P=0.009),CIP(P<0.001),LVX(P=0.003).Conclusion:1.The positive rate of cyl A,gel E,asa1,fsr in faecalis were higher than those in E.faecium,E.faecalis were more likely to possess multiple virulence genes than E.faecium.2.ace genes were mostly from urine sample,ace may cause UTI.3.In E.faecalis,the distribution of cyl A,asa1 and esp(P<0.001)were all associated with CIP.In E.faecium,the distribution of esp and acm were associated with resistance to PEN,AMP,CIP and LVX.In enterococcus strains,drug-resistance and virulence may work together to cause infection.