title: Differences in epidemiological and molecular characteristics of nasal colonization with Staphylococcus aureus (MSSA-MRSA) in children from a university hospital and day care centers.
abstract: BACKGROUND
  Clinical significance of Staphylococcus aureus colonization has been demonstrated in hospital settings; however, studies in the community have shown contrasting results regarding the relevance of colonization in infection by community-associated MRSA (CA-MRSA). In Colombia there are few studies on S. aureus colonization. The aim of this study was to determine the molecular and epidemiological characteristics of nasal colonization by S. aureus (MSSA-MRSA) in children from a university hospital and day care centers (DCCs) of Medellin, Colombia.
  
  
  METHODS
  An observational cross-sectional study was conducted in 400 children (200 in each setting), aged 0 months to 5 years, during 2011. Samples were collected from each nostril and epidemiological information was obtained from the parents. Genotypic analysis included spa typing, PFGE, MLST, SCCmec typing, detection of genes for virulence factors and agr groups.
  
  
  RESULTS
  Frequency of S. aureus colonization was 39.8% (n = 159) (hospital 44.5% and DCCs 35.0%) and by MRSA, 5.3% (n = 21) (hospital 7.0% and DCCs 3.5%). Most S. aureus colonized children were older than two years (p = 0.005), the majority of them boys (59.1%), shared a bedroom with a large number of people (p = 0.028), with history of β-Lactamase inhibitors usage (p = 0.020). MSSA strains presented the greatest genotypic diversity with 15 clonal complexes (CC). MRSA isolates presented 6 CC, most of them (47.6%) belonged to CC8-SCCmec IVc and were genetically related to previously reported infectious MRSA strains.
  
  
  CONCLUSIONS
  Differences in epidemiological and molecular characteristics between populations may be useful for the understanding of S. aureus nasal colonization dynamics and for the design of strategies to prevent S. aureus infection and dissemination. The finding of colonizing MRSA with similar molecular characteristics of those causing infection demonstrates the dissemination capacity of S. aureus and the risk of infection among the child population.
authors.affiliation: Grupo de Microbiología Molecular, Escuela de Microbiología, Universidad de Antioquia, Medellín, Colombia; Grupo de Investigación en Microbiología Básica y Aplicada - MICROBA, Escuela de Microbiología Universidad de Antioquia, Medellín, Colombia.
authors.forename: Erika A
authors.initials: EA
authors.lastname: Rodríguez
authors.affiliation: Grupo de Microbiología Molecular, Escuela de Microbiología, Universidad de Antioquia, Medellín, Colombia.
authors.forename: Margarita M
authors.initials: MM
authors.lastname: Correa
authors.affiliation: Hospital Universitario de San Vicente Fundación, Medellín, Colombia.
authors.forename: Sigifredo
authors.initials: S
authors.lastname: Ospina
authors.affiliation: Hospital Universitario de San Vicente Fundación, Medellín, Colombia.
authors.forename: Santiago L
authors.initials: SL
authors.lastname: Atehortúa
authors.affiliation: Grupo de Microbiología Molecular, Escuela de Microbiología, Universidad de Antioquia, Medellín, Colombia; Grupo de Investigación en Microbiología Básica y Aplicada - MICROBA, Escuela de Microbiología Universidad de Antioquia, Medellín, Colombia.
authors.forename: J Natalia
authors.initials: JN
authors.lastname: Jiménez
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics; D002656:Child Day Care Centers; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D005260:Female; D005838:Genotype; D006785:Hospitals, University; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics* / Q000302:isolation & purification*; D009666:Nose / Q000382:microbiology; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D015534:Trans-Activators / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics; D065093:beta-Lactamase Inhibitors / Q000627:therapeutic use
chemical_list: C095698:Agr protein, Staphylococcus aureus; D001426:Bacterial Proteins; D015534:Trans-Activators; D037521:Virulence Factors; D065093:beta-Lactamase Inhibitors