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 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.

Objective To investigate the multi-drug resistance of Klebsiella strains and its mechanism.Methods Twenty strains of Klebsiella were isolated from the Affiliated Hospital of Medical College,Ningbo University from October 2009 to March 2011,in which 18 isolates were Klebsiella pneumonia and 2 were Klebsiella planticola. Drug sensitivity was determined by K-B tests. Drug resistant genes gyrA,parC (chromosome mediated) and aac( 6′)-I b-Cr,qnrA,qnrB,qnrS,qepA (plasmid mediated) were amplified by PCR and verified by direct automated fluorogenic sequencing. Results Resistance to β-1actams,aminoglycosides and quinolones was observed in 20 strains,and resistant rates were all above 80％.Klebsiella planticola strains were sensitive to imipenem and meropenem.Mutations of gyrA and parC genes existed in 18 strains (90％),and the positive rates of aac (6') -I b-C r,qnrB and qnrS were 60％ (12/20),20％ (4/20) and 20％ (4/20),respectively.Conclusion The mutations ofgyrA and parC genes may be the main cause of the resistance to quinolones in these strains.