title: Preoperative nasal methicillin-resistant Staphylococcus aureus status, surgical prophylaxis, and risk-adjusted postoperative outcomes in veterans.
abstract: OBJECTIVE
  To determine whether preoperative nasal methicillin-resistant Staphylococcus aureus (MRSA) carriage is a significant predictor of postoperative infections, after accounting for surgical infection risk and surgical prophylaxis.
  
  
  METHODS
  Retrospective cohort study.
  
  
  METHODS
  Veterans Affairs (VA) Boston patients who had nasal MRSA polymerase chain reaction screening performed in the 31 days before clean or clean contaminated surgery in 2008-2009.
  
  
  METHODS
  Postoperative MRSA clinical cultures and infections, total surgical site infections (SSIs), and surgical prophylaxis data were abstracted from administrative databases. MRSA infections were confirmed via chart review. Multivariate analysis of risk factors for each outcome was conducted using Poisson regression. SSI risk index was calculated for a subset of 1,551 patients assessed by the VA National Surgical Quality Improvement Program.
  
  
  RESULTS
  Among 4,238 eligible patients, 279 (6.6%) were positive for preoperative nasal MRSA. Postoperative MRSA clinical cultures and infections, including MRSA SSIs, were each significantly increased in patients with preoperative nasal MRSA. After adjustment for surgery type, vancomycin prophylaxis, chlorhexidine/alcohol surgical skin preparation, and SSI risk index, preoperative nasal MRSA remained significantly associated with postoperative MRSA cultures (relative risk [RR], 8.81; 95% confidence interval [CI], 3.01-25.82) and infections (RR, 8.46; 95% CI, 1.70-42.04). Vancomycin prophylaxis was associated with an increased risk of total SSI in those negative for nasal MRSA (RR, 4.34; 95% CI, 2.19-8.57) but not in patients positive for nasal MRSA.
  
  
  CONCLUSIONS
  In our population, preoperative nasal MRSA colonization was independently associated with MRSA clinical cultures and infections in the postoperative period. Vancomycin prophylaxis increased the risk of total SSI in nasal MRSA-negative patients.
authors.affiliation: Department of Medicine, Veterans Affairs Boston Healthcare System, Boston, Massachusetts, 02132, USA. kalpana.gupta@va.gov
authors.forename: Kalpana
authors.initials: K
authors.lastname: Gupta
authors.forename: Judith
authors.initials: J
authors.lastname: Strymish
authors.forename: Youmna
authors.initials: Y
authors.lastname: Abi-Haidar
authors.forename: Sandra A
authors.initials: SA
authors.lastname: Williams
authors.forename: Kamal M F
authors.initials: KM
authors.lastname: Itani
mesh_terms: D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D019072:Antibiotic Prophylaxis / Q000706:statistics & numerical data*; D001900:Boston; D015331:Cohort Studies; D003428:Cross Infection / Q000209:etiology* / Q000517:prevention & control; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008875:Middle Aged; D015999:Multivariate Analysis; D009297:Nasal Mucosa / Q000382:microbiology*; D016012:Poisson Distribution; D012189:Retrospective Studies; D020379:Risk Adjustment; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000209:etiology* / Q000517:prevention & control; D013530:Surgical Wound Infection / Q000209:etiology* / Q000517:prevention & control; D016896:Treatment Outcome; D014640:Vancomycin / Q000627:therapeutic use; D058014:Veterans Health / Q000706:statistics & numerical data*
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin