title: Staphylococcus aureus poststernotomy mediastinitis: description of two distinct acquisition pathways with different potential preventive approaches.
abstract: OBJECTIVE
  Determining the acquisition routes of infection is crucial to designing specific preventive approaches against Staphylococcus aureus poststernotomy mediastinitis.
  
  
  METHODS
  From 2002 to 2004, a nasal sample was obtained from patients before cardiac surgery. We collected clinical and microbiologic data of all episodes of S aureus poststernotomy mediastinitis. A case-control study (3:1) was performed to confirm the role of previous preoperative nasal colonization by S aureus as a risk factor for S aureus poststernotomy mediastinitis. Pulsed field gel electrophoresis molecular analysis of nasal and surgical site S aureus isolates was performed to analyze their relatedness in each patient with poststernotomy mediastinitis and with other patients of the study cohort.
  
  
  RESULTS
  S aureus nasal cultures were positive in 228 (15.9%) of 1432 patients: methicillin-susceptible S aureus in 222 (15.5%) and meticillin-resistant S aureus in 6 (0.4%). S aureus poststernotomy mediastinitis was diagnosed in 17 (1.2%) of 1432 patients: 9 (3.95%) of 228 in colonized patients versus 8 (0.66%) of 1204 in noncolonized patients (P < .0001). Seven of 9 patients (1.2%) with methicillin-susceptible S aureus had an identical isolate by pulsed field gel electrophoresis in preoperative nasal and surgical-site cultures, but no clonal relatedness was shown among the isolates from these 9 patients. None of the 8 patients with methicillin-resistant S aureus poststernotomy mediastinitis had an identical isolate by pulsed field gel electrophoresis in preoperative nasal and surgical-site cultures, and the same clone of methicillin-resistant S aureus was responsible for all these cases.
  
  
  CONCLUSIONS
  Endogenous [corrected] nasal colonization often precedes methicillin-resistant S aureus poststernotomy mediastinitis, which suggests that preoperative [corrected] decontamination is adequate for preventing methicillin-susceptible [corrected] S aureus poststernotomy mediastinitis, whereas hospital infection control measures seem to be the major factor for preventing methicillin-resistant S aureus poststernotomy mediastinitis.
authors.affiliation: Unit of Infectious Diseases, University Hospital 12 de Octubre, Madrid, Spain. rafasjg@yahoo.es
authors.forename: Rafael
authors.initials: R
authors.lastname: San Juan
authors.forename: Fernando
authors.initials: F
authors.lastname: Chaves
authors.forename: Maria Jesus
authors.initials: MJ
authors.lastname: López Gude
authors.forename: Carmen
authors.initials: C
authors.lastname: Díaz-Pedroche
authors.forename: Joaquin
authors.initials: J
authors.lastname: Otero
authors.forename: Jose María
authors.initials: JM
authors.lastname: Cortina Romero
authors.forename: Juan Jose
authors.initials: JJ
authors.lastname: Rufilanchas
authors.forename: Jose Maria
authors.initials: JM
authors.lastname: Aguado
mesh_terms: D000368:Aged; D005260:Female; D006801:Humans; D008297:Male; D008480:Mediastinitis / Q000382:microbiology* / Q000517:prevention & control*; D009666:Nose / Q000382:microbiology; D011183:Postoperative Complications / Q000382:microbiology* / Q000517:prevention & control*; D011300:Preoperative Care; D013203:Staphylococcal Infections / Q000209:etiology* / Q000517:prevention & control*; D013211:Staphylococcus aureus / Q000302:isolation & purification; D013249:Sternum / Q000601:surgery*