Abstract： Objective To identify antimicrobial susceptibilities of community-acquired Staphylococcus aureus infections and the risk factors of severe infections.Methods Clinical data of 184 cases of community-acquired Staphylococcus aureus infections collected from 4 hospitals in Ningbo during May 2008 and May 2013 were reviewed.Microbial sensitivity test and virulence genes ( pvl and tst) detection were performed in clinical isolates, and SCCmec genotyping was performed in methicillin-resistant Staphylococcus aureus ( MRSA) strains.Binary logistic regression analysis was used to identify the risk factors for severe infections.Results Among 184 cases of community-acquired Staphylococcus aureus infections, 39 ( 21.20%) were severe cases. Staphylococcus aureus strains were highly resistant to penicillin, erythromycin and clindamycin, but more than 75% strains were sensitive to oxacillin, aminoglycosides, quinolones, rifampicin and vancomycin.Logistic regression analysis showed that advanced age (OR=1.024, 95%CI:1.005-1.043, P<0.05), malignant tumor (OR=15.288, 95%CI:1.609-145.229, P<0.05) , autoimmune diseases or long-term hormone therapy ( OR=12.102, 95%CI:2.082-70.338, P <0.01 ) were risk factors for severe community-acquired Staphylococcus aureus infections. Conclusions Strains isolated from the patients with community-acquired Staphylococcus aureus infections in&nbsp;Ningbo are usually sensitive to oxacillin, aminoglycosides, quinolones, rifampicin and vancomycin, which may be recommended for clinical use.Elder patients and those with malignant tumor, autoimmune diseases or long-term hormone therapy are more likely to develop severe Staphylococcus aureus infections.