title: Dynamics of acquisition and loss of carriage of Staphylococcus aureus strains in the community: the effect of clonal complex.
abstract: BACKGROUND
  Staphylococcus aureus nasal carriage increases infection risk. However, few studies have investigated S. aureus acquisition/loss over >1 year, and fewer still used molecular typing.
  
  
  METHODS
  1123 adults attending five Oxfordshire general practices had nasal swabs taken. 571 were re-swabbed after one month then every two months for median two years. All S. aureus isolates were spa-typed. Risk factors were collected from interviews and medical records.
  
  
  RESULTS
  32% carried S. aureus at recruitment (<1% MRSA). Rates of spa-type acquisition were similar in participants S. aureus positive (1.4%/month) and negative (1.8%/month, P = 0.13) at recruitment. Rates were faster in those carrying clonal complex (CC)15 (adjusted (a)P = 0.03) or CC8 (including USA300) (aP = 0.001) at recruitment versus other CCs. 157/274 (57%) participants S. aureus positive at recruitment returning ≥ 12 swabs carried S. aureus consistently, of whom 135 carried the same spa-type. CC22 (including EMRSA-15) was more prevalent in long-term than intermittent spa-type carriers (aP = 0.03). Antibiotics transiently reduced carriage, but no other modifiable risk factors were found.
  
  
  CONCLUSIONS
  Both transient and longer-term carriage exist; however, the approximately constant rates of S. aureus gain and loss suggest that 'never' or truly 'persistent' carriage are rare. Long-term carriage varies by strain, offering new explanations for the success of certain S. aureus clones.
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom; UBC School of Population and Public Health, British Columbia Centre for Disease Control, 655 West 12th Avenue, Vancouver, BC V5Z 4R4, Canada. Electronic address: Ruth.Miller@bccdc.ca.
authors.forename: Ruth R
authors.initials: RR
authors.lastname: Miller
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom; National Institute for Health Research Oxford Biomedical Research Centre, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: A Sarah
authors.initials: AS
authors.lastname: Walker
authors.affiliation: National Institute for Health Research Oxford Biomedical Research Centre, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom; Oxford University Hospitals National Health Service Trust, Oxford OX3 9DU, United Kingdom.
authors.forename: Heather
authors.initials: H
authors.lastname: Godwin
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom; National Institute for Health Research Oxford Biomedical Research Centre, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: Rowena
authors.initials: R
authors.lastname: Fung
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: Antonina
authors.initials: A
authors.lastname: Votintseva
authors.affiliation: National Institute for Health Research Oxford Biomedical Research Centre, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom; Department of Statistics, University of Oxford, Oxford OX1 3TG, United Kingdom; Wellcome Trust Centre for Human Genetics, Oxford OX3 7BN, United Kingdom.
authors.forename: Rory
authors.initials: R
authors.lastname: Bowden
authors.affiliation: Department of Primary Care Health Sciences, University of Oxford, Oxford OX1 2ET, United Kingdom.
authors.forename: David
authors.initials: D
authors.lastname: Mant
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom; National Institute for Health Research Oxford Biomedical Research Centre, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: Timothy E A
authors.initials: TE
authors.lastname: Peto
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom; National Institute for Health Research Oxford Biomedical Research Centre, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: Derrick W
authors.initials: DW
authors.lastname: Crook
authors.affiliation: National Institute for Health Research Oxford Biomedical Research Centre, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom; Department of Primary Care Health Sciences, University of Oxford, Oxford OX1 2ET, United Kingdom.
authors.forename: Kyle
authors.initials: K
authors.lastname: Knox
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D017720:Molecular Epidemiology; D058889:Molecular Typing; D009297:Nasal Mucosa / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013205:Staphylococcal Protein A / Q000235:genetics; D013211:Staphylococcus aureus / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D006113:United Kingdom / Q000453:epidemiology; D055815:Young Adult
chemical_list: D013205:Staphylococcal Protein A
keywords: Carriage duration; Colonisation; Molecular epidemiology; Staphylococcus aureus; spa-typing