Objective To explore the relationship between biofilm formation ability and virulence of vari-ous drug-resistant strains of Staphylococcus aureus(SA)in bloodstream infections.Methods A total of 42 strains of bloodstream infection SA were collected and identified and tested for drug sensitivity using the BDM50 automatic bacterial identification drug susceptibility system.The biofilm formation ability was deter-mined by crystal violet staining.The virulence was evaluated by detecting extracellular lipase,extracellular protease,and hemolysin,as well as conducting a toxicity test with Galleria mellonella larvae.Results Among the 42 strains of bloodstream infection SA,there were 16 strains(38.10%)of methicillin-resistant Staphylo-coccus aureus(MRSA).Among the 42 bloodstream infected SA strains,25 strains(59.50%)had the ability to form biofilms,among which there were 18 strains of methicillin-sensitive Staphylococcus aureus(MSSA)and 7 strains of MRSA.Among the 42 SA strains with bloodstream infection,37 strains(88.10%)produced hemolysin,18 strains(42.90%)produced extracellular protease,and no strains produced extracellular lipase.The Galleria mellonella larvae toxicity test showed that MRSA had stronger virulence than MSSA.Conclusion Compared with MSSA,MRSA has a higher proportion of extracellular enzymes produced,stronger virulence,and relatively weaker ability to form biofilms.