title: Changes in the nasal colonization with methicillin-resistant Staphylococcus aureus in children: 2004-2009.
abstract: BACKGROUND
  Staphylococcus aureus is an important cause of infection, particularly in persons colonized with this organism. This study compared the annual prevalence and microbiological characteristics of methicillin-resistant S. aureus (MRSA) nasal colonization in Taiwanese children from 2004 through 2009. Risk factors for MRSA were determined for the overall study period.
  
  
  METHODS
  Children from birth to ≤14 years of age presenting for health maintenance visits or attending 1 of 57 kindergartens were recruited. Nasal swabs were obtained, and a questionnaire was administered. The prevalence and microbiological characteristics of MRSA colonization were also calculated for two 3-year periods: 2004-2006 and 2007-2009.
  
  
  RESULTS
  Cultures of the anterior nares were positive for S. aureus in 824 (25.8%) of the 3,200 children, and MRSA colonization was found in 371 (11.6%) children. The prevalence of S. aureus colonization decreased from 28.1% in 2004-2006 to 23.3% in 2007-2009 (p<0.01), whereas the prevalence of MRSA colonization increased from 8.1% to 15.1% during this period (p<0.0001). Multivariate analysis revealed that the independent risk factors for MRSA carriage were different for male and female children, and also among age groups. Most MRSA isolates belonged to sequence type 59 (ST59) (86.3%); however, a multiresistant MRSA clone with ST338 background emerged in 2007-2009. Ten (62.5%) of the 16 MRSA isolates expressed the genotypic profile ST338/staphylococcal cassette chromosome mec V(T)/Panton-Valentine leukocidin-positive/staphylococcal enterotoxin B-positive, and differed only in their antimicrobial susceptibility patterns.
  
  
  CONCLUSIONS
  The prevalence of nasal colonization by MRSA increased among healthy Taiwanese children from 2004-2006 to 2007-2009, despite an overall decrease in the prevalence of nasal colonization by S. aureus. A multiresistant MRSA clone characterized as ST338 was identified from these children.
authors.affiliation: Department of Pediatrics, Tri-Service General Hospital, National Defense Medical Center, Taipei, Taiwan. drluoped@yahoo.com.tw
authors.forename: Wen-Tsung
authors.initials: WT
authors.lastname: Lo
authors.forename: Chih-Chien
authors.initials: CC
authors.lastname: Wang
authors.forename: Wei-Jen
authors.initials: WJ
authors.lastname: Lin
authors.forename: Sheng-Ru
authors.initials: SR
authors.lastname: Wang
authors.forename: Ching-Shen
authors.initials: CS
authors.lastname: Teng
authors.forename: Ching-Feng
authors.initials: CF
authors.lastname: Huang
authors.forename: Shyi-Jou
authors.initials: SJ
authors.lastname: Chen
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D005260:Female; D005838:Genotype; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D008712:Methicillin / Q000494:pharmacology*; D055624:Methicillin-Resistant Staphylococcus aureus / Q000378:metabolism*; D009666:Nose / Q000382:microbiology*; D011446:Prospective Studies; D013203:Staphylococcal Infections / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000378:metabolism*; D013624:Taiwan
chemical_list: D008712:Methicillin