Detection of virulence genes and biofilm formation of Enterococci strains isolated from blood samples
Objective To detect the main virulence genes and biofilm formation of Enterococci strains isolated from blood samples .Methods Twenty-eight strains of Enterococcus faecalis （ E.faecalis） and 54 strains of Enterococcus faecium （ E.faecium） were collected from blood samples .Five main virulence genes （asa1, esp, hyl, cylA and gelE） were detected by multiplex PCR.Biofilm formation was investigated by using microtiter dish biofilm formation assay .Results All E.faecalis strains were positive for at least one kind of virulence genes , of which 14 strains were concurrently positive for asa1, esp, cylA and gelE.asa1, cylA and gelE were only detected in E.faecalis strains, while hyl gene only existed in E.faecium strains. Twenty-seven strains of E.faecium were esp positive, of which 12 strains were both hyl and esp positive. None of the 5 virulence genes were identified in 10 strains of E.faecium.85.7% of E.faecalis strains and 63.0%of E.faecium strains could form biofilm.Conclusion Compared with E.faecium strains, more types of virulence genes were detected in E.faecalis strains with higher positive rates .Moreover , E.faecalis strains were more likely to form biofilms than E.faecium strains. 
 
Key words: 
Enterococcus;  Virulence gene;  Multiplex PCR;  Biofilm