title: Prevalence of Staphylococcus aureus protein A (spa) mutants in the community and hospitals in Oxfordshire.
abstract: BACKGROUND
  Staphylococcal protein A (spa) is an important virulence factor which enables Staphylococcus aureus to evade host immune responses. Genotypes known as "spa-types", based on highly variable Xr region sequences of the spa-gene, are frequently used to classify strains. A weakness of current spa-typing primers is that rearrangements in the IgG-binding region of the gene cause 1-2% of strains to be designated as "non-typeable".
  
  
  RESULTS
  We developed an improved primer which enabled sequencing of all strains, containing any type of genetic rearrangement, in a large study among community carriers and hospital inpatients in Oxfordshire, UK (6110 isolates). We identified eight novel spa-gene variants, plus one previously described. Three of these rearrangements would be designated "non-typeable" using current spa-typing methods; they occurred in 1.8% (72/3905) asymptomatically carried and 0.6% (14/2205) inpatient S. aureus strains. Some individuals were simultaneously colonized by both formerly non-typeable and typeable strains; previously such patients would have been identified as carrying only currently typeable strains, underestimating mixed carriage prevalence and diversity. Formerly non-typeable strains were found in more spa-types associated with multilocus sequence type ST398 (35%), common among livestock, compared to other groups with any non-typeable strains (1-4%), suggesting particular spa-types may have been under-represented in previous human studies.
  
  
  CONCLUSIONS
  This improved method allows us to spa-type previously non-typeable strains with rearrangements in the spa-gene and to resolve cases of mixed colonization with deletions in one or more strains, thus accounting for hidden diversity of S. aureus in both community and hospital environments.
authors.affiliation: Nuffield Department of Clinical Medicine, University of Oxford, John Radcliffe Hospital, Level 7, Room 7724, Oxford OX3 9DU, United Kingdom. votintse@stats.ox.ac.uk.
authors.forename: Antonina A
authors.initials: AA
authors.lastname: Votintseva
authors.forename: Rowena
authors.initials: R
authors.lastname: Fung
authors.forename: Ruth R
authors.initials: RR
authors.lastname: Miller
authors.forename: Kyle
authors.initials: K
authors.lastname: Knox
authors.forename: Heather
authors.initials: H
authors.lastname: Godwin
authors.forename: David H
authors.initials: DH
authors.lastname: Wyllie
authors.forename: Rory
authors.initials: R
authors.lastname: Bowden
authors.forename: Derrick W
authors.initials: DW
authors.lastname: Crook
authors.forename: A Sarah
authors.initials: AS
authors.lastname: Walker
mesh_terms: D017931:DNA Primers / Q000235:genetics; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D006761:Hospitals; D006801:Humans; D008969:Molecular Sequence Data; D058889:Molecular Typing / Q000379:methods*; D009154:Mutation; D015995:Prevalence; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000382:microbiology*; D013205:Staphylococcal Protein A / Q000235:genetics*; D013211:Staphylococcus aureus / Q000145:classification* / Q000235:genetics* / Q000302:isolation & purification; D006113:United Kingdom
chemical_list: D017931:DNA Primers; D004269:DNA, Bacterial; D013205:Staphylococcal Protein A