title: Surgical Site Infections in Orthopaedic Surgery Demonstrate Clones Similar to Those in Orthopaedic Staphylococcus aureus Nasal Carriers.
abstract: BACKGROUND
  Staphylococcus aureus is the main microbial pathogen in orthopaedic infections, and it adds considerable extra costs to the national health-care system each year. Nasal carriers of Staphylococcus aureus have an increased risk of invasive disease, including surgical site infection. The purpose of the present study was to investigate whether the Staphylococcus aureus carrier clones found in patients undergoing elective orthopaedic surgery were the same as the clones found in isolates from orthopaedic patients with Staphylococcus aureus surgical site infections.
  
  
  METHODS
  Patients admitted for elective orthopaedic surgery underwent nasal cultures for Staphylococcus aureus. Further, orthopaedic patients with a deep surgical site infection caused by Staphylococcus aureus were characterized using the same genotyping methods: multilocus sequence typing and staphylococcal protein A typing.
  
  
  RESULTS
  Multilocus sequence typing revealed a large number of genotypes in the two populations. However, 85% of nasal carriers and 90% of surgical site infection isolates could be classified into the same four multilocus sequence typing clonal complexes. The risk of Staphylococcus aureus surgical site infection in nasal carriers compared with non-carriers was 5.8 times higher (95% confidence interval, 1.5 to 23.1 times). Of the nasal carriers, 6.3% (95% confidence interval, 1.7% to 10.9% [seven of 111 patients]) developed a deep Staphylococcus aureus surgical site infection, and all but one patient had identical genotypes in the nasal and surgical site infection isolates.
  
  
  CONCLUSIONS
  Staphylococcus aureus isolates from nasal carriers and patients with surgical site infection clustered into the same few multilocus sequence typing clonal complexes. This finding confirms the existence of some commonly occurring Staphylococcus aureus clones in different population groups within a geographically restricted area. The almost complete individual concordance between Staphylococcus aureus genotypes in carriers who developed a deep surgical site infection strongly supports transmission from the nose, skin surfaces, and other endogenous body regions as a possible route.
  
  
  CONCLUSIONS
  Surgical site infections might be more frequently caused by endogenous transmission than was previously assumed. Perioperative preventive efforts must focus more on this route to further decrease the risk of postoperative orthopaedic infections.
authors.affiliation: Departments of Orthopedic Surgery (I.S. and A.A.) and Clinical Molecular Biology and Laboratory Sciences (EpiGen) (I.S. and A.E.F.M.), Division of Surgery, Akershus University Hospital, Sykehusvn 25, N-1478 Lørenskog, Norway. E-mail address for I. Skråmm: inge.skramm@medisin.uio.no.
authors.forename: Inge
authors.initials: I
authors.lastname: Skråmm
authors.affiliation: Departments of Orthopedic Surgery (I.S. and A.A.) and Clinical Molecular Biology and Laboratory Sciences (EpiGen) (I.S. and A.E.F.M.), Division of Surgery, Akershus University Hospital, Sykehusvn 25, N-1478 Lørenskog, Norway. E-mail address for I. Skråmm: inge.skramm@medisin.uio.no.
authors.forename: Aina E
authors.initials: AE
authors.lastname: Fossum Moen
authors.affiliation: Departments of Orthopedic Surgery (I.S. and A.A.) and Clinical Molecular Biology and Laboratory Sciences (EpiGen) (I.S. and A.E.F.M.), Division of Surgery, Akershus University Hospital, Sykehusvn 25, N-1478 Lørenskog, Norway. E-mail address for I. Skråmm: inge.skramm@medisin.uio.no.
authors.forename: Asbjørn
authors.initials: A
authors.lastname: Årøen
authors.affiliation: Department of Infection Prevention, Oslo University Hospital, Kirkevn 166, Postboks 4950, Nydalen, N-0424 Oslo, Norway.
authors.forename: Geir
authors.initials: G
authors.lastname: Bukholm
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015373:Bacterial Typing Techniques; D002353:Carrier State / Q000382:microbiology*; D002999:Clone Cells; D005260:Female; D005838:Genotype; D006801:Humans; D008297:Male; D008875:Middle Aged; D009666:Nose / Q000382:microbiology*; D009985:Orthopedics; D011446:Prospective Studies; D012307:Risk Factors; D013211:Staphylococcus aureus / Q000145:classification* / Q000302:isolation & purification*; D013530:Surgical Wound Infection / Q000382:microbiology*