title: [Distribution of Staphylococcus aureus strains colonized in healthy community population and molecular epidemiological characteristics for MRSA strains].
abstract: OBJECTIVE
  To investigate the nasal colonization of Staphylococcus (S.) aureus strains among medical university students in Shenyang and to study the molecular epidemiological characteristics of methicillin resistant S. aureus (MRSA) strains.
  
  
  METHODS
  Sterilized nasal swabs were used to collect nasal bacteria from both nares of the students. Nasal specimens were further identified as S. aureus strains, sensitive or resistant to methicillin through a series of tests. Molecular related methods including staphylococcal cassette chromosome mec (SCCmec) typing, pulsed- field gel electrophoresis (PFGE), coagulase isotyping and minimum inhibitory concentration (MIC) determination etc. were used to characterize the isolates. Prevalence of the panton-valentine leukocidin (pvl) genes (lukS and F-PV) among the isolates was also assessed.
  
  
  RESULTS
  Staphylococci were found in 488 specimens from 977 participants through the surveillance program, conducted in 2009. Of the 488 specimens being tested, 364 were identified as coagulase-negative staphylococci (CoNS) and 124 as S. aureus. MRSA strain among the S. aureus isolates was accounted for 3.4%. In the surveillance program conducted in 2010, staphylococci grew in 310 specimens from 657 participants. Of the 310 specimens tested, 195 were identified as CoNS and 115 as S. aureus. The percentage of MRSA strains among the S. aureus isolates was 7.7%. In total, 239 students carried S. aureus, and the percentage of MRSA carriers among the total specimens tested in this study was 5.1%. Most of the MRSA strains could be classified into one of the five types of SCCmec elements. Type IV a SCCmec strains were most frequent seen overall (10 isolates). A total of 11 pulsotype were identified among the MRSA strains and were classified into 7 major groups (A to G) by the mutual correlations of their banding patterns. Ten MRSA strains were identified as pvl positive strains.
  
  
  CONCLUSIONS
  An MRSA clone (IV a SCCmec pulsotype A) carrying pvl toxin gene was found to be prevalent in the nares of the healthy university students.
authors.affiliation: Department of Medical Microbiology and Parasitology, College of Basic Medical Sciences, China Medical University, Shenyang 110001, China.
authors.forename: Xiao-xue
authors.initials: XX
authors.lastname: Ma
authors.forename: En-jie
authors.initials: EJ
authors.lastname: Luo
mesh_terms: D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D002681:China / Q000453:epidemiology; D005260:Female; D005798:Genes, Bacterial; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification*; D017720:Molecular Epidemiology; D013211:Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification*; D013334:Students; D055815:Young Adult