Molecular characterization of Staphylococcus aureus collected from 2004 to 2010 in patients with blood stream infection / 中华检验医学杂志

ABSTRACT

Objective To investigate the clonal types of Staphylococcus aureus collected from 2004to 2010 in patients with blood stream infection from a Grade A tertiary care hospital in Shanghai as well as the dynamic changes and to detect the variation in antimicrobial resistance and virulence-gene content in different strain types.Methods A total of 103 nonduplicate S.aureus isolates were collected from 2004 to 2010 from inpatients with S.aureus blood stream infection from Shanghai Huashan hospital.Determination of oxacillin MICs and the type of SCCmec gene were used to screen MRSA.Typing of S.aureus isolates was identified by using multilocus sequence typing(MLST) and S.aureus-specific staphylococcal protein A typing(spa typing),PCR was used to detect the antimicrobial resistance and virulence-gene.Results Sixtysix isolates(64.1%) MRSA were detected in 103 nonduplicate S.aureus isolates,and 35 isolates were MRSA with SCCmec type Ⅱ ,Twenty-nine isolates were MRSA with SCCmec type Ⅱ,two isolates were MRSA with SCCmec type Ⅳ,Thirty-seven isolates(35.9%) were MSSA.Thirty-three MRSA isolates were ST5,Twenty-nine MRSA isolates were ST239,two MRSA isolates were ST59,one MRSA isolates was ST641 and one MRSA isolates was ST6.All of the other clones belonged to MSSA.The percentage of ST5 and ST239 were decreased significantly after 2009(ST5 was decreased from 52.9% to 15.4%; ST239 was decreased from 61.1% to 15.4%),and new clonal types MSSA increased significantly(in 2009,the percentage of ST7 was 41.7%; new clonal types such as ST188 and ST15 were detected in 2010).In 2010,it was shown that 84.6% of MSSA were isolated from S.aureus blood stream infection,nineteen isolates(18.4%) harbored mupA gene and 41 isolates(39.8%) harbored qacA/B gene in 103 nonduplicate S.aureus isolates.It was shown that 70.6% ST239 harbored qacA/B gene.Four isolates of ST398 and 1 isolates of ST9were detected which were originally from animal.There was no significant difference of the virulence gene presence in the same strain types except sasX、lukSF and arcA genes,but there were a lot of genes which were restricted to different genomic background.Conclusions The percentage of ST5 and ST239 were decreased and new clonal types of MSSA were increased significantly in S.aureus blood stream infection,antimicrobial resistance and virulence-gene were restricted to different clonal types.