title: Risk of acquiring antibiotic-resistant bacteria from prior room occupants.
abstract: BACKGROUND
  Environmental contamination with methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) occurs during the care of patients harboring these organisms and may increase the risk of transmission to subsequent room occupants.
  
  
  METHODS
  Twenty-month retrospective cohort study of patients admitted to 8 intensive care units performing routine admission and weekly screening for MRSA and VRE. We assessed the relative odds of acquisition among patients admitted to rooms in which the most recent occupants were MRSA positive or VRE positive, compared with patients admitted to other rooms.
  
  
  RESULTS
  Of 11 528 intensive care unit room stays, 10 151 occupants were eligible to acquire MRSA, and 10 349 were eligible to acquire VRE. Among patients whose prior room occupant was MRSA positive, 3.9% acquired MRSA, compared with 2.9% of patients whose prior room occupant was MRSA negative (adjusted odds ratio, 1.4; P = .04). VRE, Among patients whose prior room occupant was VRE positive, these values were 4.5% and 2.8% respectively (adjusted odds ratio, 1.4; P = .02). These excess risks accounted for 5.1% of all incident MRSA cases and 6.8% of all incident VRE cases, with a population attributable risk among exposed patients of less than 2% for either organism. Acquisition was significantly associated with longer post-intensive care unit length of stay.
  
  
  CONCLUSIONS
  Admission to a room previously occupied by an MRSA-positive patient or a VRE-positive patient significantly increased the odds of acquisition for MRSA and VRE. However, this route of transmission was a minor contributor to overall transmission. The effect of current cleaning practices in reducing the risk to the observed levels and the potential for further reduction are unknown.
authors.affiliation: Departments of Medicine and Infection Control, Brigham and Women's Hospital and Harvard Medical School, Boston, MA 02115, USA. sshuang@partners.org
authors.forename: Susan S
authors.initials: SS
authors.lastname: Huang
authors.forename: Rupak
authors.initials: R
authors.lastname: Datta
authors.forename: Richard
authors.initials: R
authors.lastname: Platt
mesh_terms: D001900:Boston / Q000453:epidemiology; D002353:Carrier State; D015331:Cohort Studies; D003428:Cross Infection / Q000453:epidemiology / Q000382:microbiology*; D016983:Enterococcus; D005260:Female; D016908:Gram-Positive Bacterial Infections / Q000453:epidemiology / Q000635:transmission*; D006760:Hospitalization; D006801:Humans; D007362:Intensive Care Units; D008297:Male; D016106:Methicillin Resistance; D008875:Middle Aged; D016017:Odds Ratio; D010362:Patients' Rooms; D012189:Retrospective Studies; D012306:Risk; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000635:transmission*; D013211:Staphylococcus aureus; D020713:Vancomycin Resistance