title: Epidemiology of methicillin-resistant Staphylococcus aureus carriage and MRSA surgical site infections in patients undergoing colorectal surgery: a cohort study in two centers.
abstract: BACKGROUND
  Surgical site infections (SSIs) after colorectal surgery usually are caused by commensal intestinal bacteria. Methicillin-resistant Staphylococcus aureus (MRSA) may be responsible for additional SSI-related morbidity. The aim of this retrospective cohort study was to describe the epidemiology of SSIs caused by MRSA after colorectal surgery in two tertiary-care centers, one in Geneva, Switzerland (G), and the other in Chicago, Illinois (C).
  
  
  METHODS
  Adult patients undergoing colorectal resections during periods of universal screening for MRSA on admission were identified retrospectively. Demographic characteristics, surgery-related factors, and occurrence of MRSA SSI were compared in patients with and without MRSA carriage before surgery.
  
  
  RESULTS
  There were 1,069 patients (G=194, C=875) with a median age of 67 years fulfilling the inclusion criteria. Of these, 45 patients (4.2%) had a positive MRSA screening result within 30 days before surgery (G=18, C=27; p<0.001). Ten patients (0.9%; G=6, C=4) developed MRSA SSI, detected a median of 17.5 days after surgery, but only two of them were MRSA-positive before surgery. Nine of the 45 MRSA carriers identified by screening received pre-operative prophylaxis with vancomycin (G 6/18, C 3/27), and 17 of these patients (37.8%; G 7/18, C 10/27) were started on MRSA decolonization therapy before surgery. Pre-operative administration of either decolonization or vancomycin was not protective against MRSA SSI (p=0.49).
  
  
  CONCLUSIONS
  Methicillin-resistant S. aureus seems to be an infrequent cause of SSI after colorectal resections, even in MRSA carriers. Systematic universal screening for MRSA carriage prior to colorectal surgery may not be beneficial for the individual patient. Post-operative factors seem to be important in MRSA infections, as the majority of MRSA SSIs occurred in patients negative for MRSA carriage.
authors.affiliation: Infection Control Program, Geneva University Hospitals and Faculty of Medicine, Geneva, Switzerland.
authors.forename: Benedikt
authors.initials: B
authors.lastname: Huttner
authors.forename: Ari A
authors.initials: AA
authors.lastname: Robicsek
authors.forename: Pascal
authors.initials: P
authors.lastname: Gervaz
authors.forename: Eli N
authors.initials: EN
authors.lastname: Perencevich
authors.forename: Eduardo
authors.initials: E
authors.lastname: Schiffer
authors.forename: Jacques
authors.initials: J
authors.lastname: Schrenzel
authors.forename: Stephan
authors.initials: S
authors.lastname: Harbarth
mesh_terms: D000368:Aged; D002353:Carrier State / Q000453:epidemiology* / Q000382:microbiology; D016009:Chi-Square Distribution; D003106:Colon / Q000601:surgery; D013505:Digestive System Surgical Procedures / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D012007:Rectum / Q000601:surgery; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013530:Surgical Wound Infection / Q000453:epidemiology* / Q000382:microbiology; D013557:Switzerland / Q000453:epidemiology; D014481:United States / Q000453:epidemiology