title: Dynamic pattern and genotypic diversity of Staphylococcus aureus nasopharyngeal carriage in healthy pre-school children.
abstract: OBJECTIVE
  It is common wisdom that persistent carriage of Staphylococcus aureus is more frequent in young children than in adults. The objectives of this study were to assess the S. aureus temporal carriage pattern among a healthy community of pre-school children, with concomitant description of genotype diversity, toxin-encoding genes and antibiotic resistance.
  
  
  METHODS
  Among 333 children 3-6 years of age, S. aureus nasopharyngeal carriage was assessed over one school year by culture of three sequential nasopharyngeal aspirates. Identification, methicillin resistance and toxin production profile were determined by PCR. Genotyping was performed by spa sequencing and multilocus sequence typing (MLST).
  
  
  RESULTS
  Out of 830 samples collected, 286 (34%) yielded S. aureus from 185 carriers (55%). Based on consecutive genotype analysis, only 40/268 (15%) children could be classified as persistent carriers, and the remaining 118 (44%) showed intermittent carriage. spa typing revealed 82 types clustered into 13 spa clonal complexes (CCs). Fourteen strains isolated from 11 (3%) children were methicillin-resistant S. aureus (MRSA), half of these strains belonged to the commonly hospital-associated spa t008-ST8-SCCmec IV. Methicillin-susceptible S. aureus (MSSA) were genotypically more diverse. Toxic shock syndrome toxin and egc1/2 complexes were highly prevalent (24%). Contrastingly, Panton-Valentine leucocidin (PVL) was carried only by three MSSA strains (0.6% of children). Exfoliative toxins were detected in 10 (3.5%) MSSA strains, of which 5 were related to the impetigo clone CC121.
  
  
  CONCLUSIONS
  Although S. aureus nasopharyngeal carriage was high among healthy pre-school children, persistent carriage seems to be less frequent than previously reported. The prevalence of MRSA carriage was 3%, but was not associated with PVL.
authors.affiliation: Paediatric Infectious Diseases Department, Hôpital Universitaire des Enfants Reine Fabiola, Brussels, Belgium. sophie.blumental@ulb.ac.be
authors.forename: S
authors.initials: S
authors.lastname: Blumental
authors.forename: A
authors.initials: A
authors.lastname: Deplano
authors.forename: S
authors.initials: S
authors.lastname: Jourdain
authors.forename: R
authors.initials: R
authors.lastname: De Mendonça
authors.forename: M
authors.initials: M
authors.lastname: Hallin
authors.forename: C
authors.initials: C
authors.lastname: Nonhoff
authors.forename: S
authors.initials: S
authors.lastname: Rottiers
authors.forename: A
authors.initials: A
authors.lastname: Vergison
authors.forename: O
authors.initials: O
authors.lastname: Denis
mesh_terms: D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology*; D002648:Child; D002675:Child, Preschool; D024881:Drug Resistance, Bacterial; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D058885:Multilocus Sequence Typing; D009305:Nasopharynx / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D037521:Virulence Factors / Q000235:genetics
chemical_list: D037521:Virulence Factors
keywords: MRSA; carriers; kindergarten