title: Influence of host genetics and environment on nasal carriage of staphylococcus aureus in danish middle-aged and elderly twins.
abstract: BACKGROUND
  Nasal carriage is a major risk factor for Staphylococcus aureus infection. Approximately, one-quarter of adults carry S. aureus. However, the role of host genetics on S. aureus nasal carriage is unknown.
  
  
  METHODS
  Nasal swabs were obtained from a national cohort of middle-aged and elderly Danish twins. Subjects colonized with S. aureus were identified by growth on selective plates and spa typing. A second sample was obtained from twins initially concordant for carriage. Twins found to again be colonized with S. aureus were defined as persistent carriers.
  
  
  RESULTS
  The prevalence of S. aureus carriage among 617 twin pairs (monozygotic/dizygotic pairs: 112/505) was 26.3% (95% confidence interval [CI], 24.0%-28.9%). The concordance rate for carriage did not differ significantly between pairs of monozygotic (37.5%; 95% CI, 22.3%-53.8%) twins and same sex (24.2%; 95% CI, 15.4%-34.5%), and opposite sex (21.4%; 95% CI, 12.0%-33.4%) dizygotic twins. Despite shared childhoods, only 1 of 617 pairs was concordant with respect to lineage. Although heritability increased for S. aureus and lineage persistency, no significant heritability was detected.
  
  
  CONCLUSIONS
  In this study, host genetic factors exhibited only a modest influence on the S. aureus carrier state of middle-aged and elderly individuals.
authors.affiliation: Microbiology and Infection Control, Statens Serum Institut, Copenhagen S, Denmark. psa@ssi.dk
authors.forename: Paal Skytt
authors.initials: PS
authors.lastname: Andersen
authors.forename: Jacob Krabbe
authors.initials: JK
authors.lastname: Pedersen
authors.forename: Peder
authors.initials: P
authors.lastname: Fode
authors.forename: Robert L
authors.initials: RL
authors.lastname: Skov
authors.forename: Vance G
authors.initials: VG
authors.lastname: Fowler
authors.forename: Marc
authors.initials: M
authors.lastname: Stegger
authors.forename: Kaare
authors.initials: K
authors.lastname: Christensen
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002353:Carrier State / Q000453:epidemiology*; D003718:Denmark; D004783:Environmental Microbiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D058889:Molecular Typing; D015995:Prevalence; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000235:genetics*; D013211:Staphylococcus aureus / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D014427:Twins