| ObjectiveMethicillin-resistant Staphylococcus aureus (MRSA), often with multiple drug resistance, is a major human pathogen capable of causing hospital-associated infections, which is a serious clinical problem worldwide. The genotype distribution of MRSA differs in different geographical regions. Therefore, adequate understanding of genotypic characteristics and evolutionary pathway of endemic MRSA isolates in this region, which allows monitoring of local outbreaks and wider-scale dissemination of specific dangerous clones, is of now paramount importance.The aim of this study was to investigate the genotypic characteristics and evolutionary pattern of MRSA clones in Shenyang by using SCCmec typing, MLST, and Spa typing.This study will play an important role in tracking the genetic changes to chart the emergence, spread and evolution of MRSA in this region.Method1.Bacterial isolates:A total of 104 MRSA isolates were recovered from patients presenting with symptoms consistent with MRSA infection by the clinical microbiology laboratory in five hospitals in Liaoning between 2002 and 2008, Included The First Hospital of China Medical University, Shengjing Hospital, Liaoning Provincial People's Hospital, Dalian Central Hospital, The First Hospital of Dalian Medical University.2.SCCmec genotyping:SCCmec typing was done by PCR by using the primers mec complex and ccr gene complex and sequencing.3. Panton-Valentine leukocidin (PVL):PCR method amplified characteristics gene, confirmation on the Internet after sequencing;4. Multi-locus sequence typing (MLST):MLST was performed according to the recommended method by PCR. Each primer pair amplified an internal fragment of seven housekeeping genes. All PCR products were sequenced in both directions. The allele types and the resulting STs were assigned at the S. aureus. MLST database via the Internet (www.mlst.net). Sequence types were clustered into groups by eBURST analysis.5. Staphylococcal protein A gene polymorphism analysis (spa):Typing of spa was amplified by using the primers spa-1096f and spa-1517r. Spa types were assigned by the database (http://www.ridom.de/spaserver/).Results1. SCCmec typing:MRS A isolated were SCCmecâ…¡,â…¢type mainly in Liaoning Province,accounted for 50% and 45.2% each. The mainly infection of MRSA was SCCmecâ…¢type in The First Hospital of China Medical University, accounted for 61.8% of this hospital isolates; Other four teaching hospitals were mainly typeâ…¡. The SCCmecâ…¡of MRSA was 100% in the First Hospital of Dalian Medical University. Meanwhile, five CA-MRSA strains was found in the Shenyang area(SCCmecâ…£was 3, isolated in the First Hospital of China Medical University; SCCmec V was 2, the First Hospital of China Medical University and Shengjing Hospital was 1 respectively.2. PVL toxin:Only three SCCmecâ…£type community MRSA strains were positive and the remained 101 were negative for PVL toxin;3. MLST typing:Selected 25 MRSA strains were MLST genotyping,(SCCmecâ…¡type was 7 strains, SCCmecâ…¢was 13 strains, and five CA-MRSA), HA-MRSA strains was ST239 mainly, followed by ST5, CA-MRSA was ST59 mainly, followed by ST7 and one CA-MRSA genotype failed;4. spa typing:The first Hospital of China Medical University was mainly t030, accounted for 56.4% in this hospital; Shengjing hospital was mainly t570 and t030, accounted for 33.3% each; The first Hospital of Dalian Medical University was t002 and accounting for 86.7% in this hospital separation rate, Dalian Central Hospital was t002 and accounted for 66.7%; The first People's Hospital of Liaoning Provincial was t002 and accounted for 60%.Conclusion1.MRSA isolates was mainly SCCmecâ…¢-t030 and SCCmecâ…¡-t002 in Liaoning region, and was a popular trend in alternative;2. The emergence of CA-MRSA strains suggested that MRSA has spread trends From hospitals to community in Liaoning;3. CA-MRSA was more easy to carry PVL toxin than HA-MRSA, suggested it greater virulence.
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