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Primary Investigation of the Virulence Factors of vancomycin-resistant Enterococcus faecium in a tertiary-care hospital of Sichuan, China hospital Yao Deng, Zhenhui Li, Yanchun Huang, Yulin Xiao, Chao He,Xie Yi, Mei Kang, Hong Fan Division of Clinical Microbiology, Department of Laboratory Medicine, West china Hospital SiChuan University. ChengDu SiChuan 610041 Keywords: vancomycin-resistance Enterococcus faecium; virulence gene; Antibiotic resistance Corresponding author: Mei kang, Hong Fan Abstract Objective Objective To analyze the phenotypic and molecular characterization of vancomycin- resistant Enterococcus faecium(VREFm) isolates, and figure out the potential association of the three virulence factors: enterococcal surface protein (esp); hyaluronidase (hyl); adhesin of collagen from E. faecium(acm) with the colonization or infection of E.faecium. Methods VREFm isolates(n=45) from intestinal colonization of patients in Intensive Care Unit(ICU) had been screened by VRE chromogenic agar and identified by multiplex polymerase chain reaction(PCR) for the D-Ala-D-Ala ligase gene(ddl gene). Infective ampocillin-resistant vancomycin-susceptible E.faecium (VSEFm) isolates(n=60) and infective VREFm isolates (n=8) had been identified by Vitek II compact. Use E-test to detect the minimum inhibitory concentrations (MICs)of VREFm. The vancomycin-resistant genes and the virulence factors(hyl、esp、acm) were detected by PCR. Results 53 VREFm strains(8 infective strains and 45 intestinal colonization strains) and 60 VSEFm strains over 1 year period were collected. 34 VSEFm strains from blood, other 26 VSEFm strains from pleural fluid and CSF. All the 53 VREFm isolates harbored the vanA gene and exhibited the VanA phenotype. 37 of 45(82.22%) intestinal colonization VREFm strains, all the 8 clinical infective VREFm strains and 32 of 60(53.33%) clinical infective VSEFm strains carried the esp gene. 21 of 45(46.67%) intestinal colonization VREFm strains, 3 of 8(37.5%) clinical infective VREFm strains and 17 of 60(28.3%) clinical infective VSEFm strains carried the hyl gene. 41 of 45(91.11%) intestinal colonization VREFm strains, 6 of 8(75%)clinical infective VREFm strains carried the acm gene, compared with 55% acm-positive in clinical infective VSEFm strains .In VREFm group, 21of 24(87.5%) hyl-positive strains carried the esp gene, however, in VSE group, only 5 of 17(29.41%) hyl-positive strains carried the esp gene. In addition, the positive rate of acm gene in VSEFm strains from blood(32.35%) is much lower than that from the pleural fluid and CSF (84.62%). Conclusion Esp、hyl and acm are highly related to the infection of E.faecium. Especially for VREFm, the esp and acm gene are more related to its infection or colonization than hyl gene. A further research will be carry out to confirm whether esp can help the E.faecium resistant to antibiotic in hyl-positive strains and whether acm can help the E.faecium invading the serous cavity.