title: Methicillin-resistant Staphylococcus aureus infection and hospitalization in high-risk patients in the year following detection.
abstract: BACKGROUND
  Many studies have evaluated methicillin-resistant Staphylococcus aureus (MRSA) infections during single hospitalizations and subsequent readmissions to the same institution. None have assessed the comprehensive burden of MRSA infection in the period after hospital discharge while accounting for healthcare utilization across institutions.
  
  
  RESULTS
  We conducted a retrospective cohort study of adult patients insured by Harvard Pilgrim Health Care who were newly-detected to harbor MRSA between January 1991 and December 2003 at a tertiary care medical center. We evaluated all MRSA-attributable infections associated with hospitalization in the year following new detection, regardless of hospital location. Data were collected on comorbidities, healthcare utilization, mortality and MRSA outcomes. Of 591 newly-detected MRSA carriers, 23% were colonized and 77% were infected upon detection. In the year following detection, 196 (33%) patients developed 317 discrete and unrelated MRSA infections. The most common infections were pneumonia (34%), soft tissue (27%), and primary bloodstream (18%) infections. Infections occurred a median of 56 days post-detection. Of all infections, 26% involved bacteremia, and 17% caused MRSA-attributable death. During the admission where MRSA was newly-detected, 14% (82/576) developed subsequent infection. Of those surviving to discharge, 24% (114/482) developed post-discharge infections in the year following detection. Half (99/185, 54%) of post-discharge infections caused readmission, and most (104/185, 55%) occurred over 90 days post-discharge.
  
  
  CONCLUSIONS
  In high-risk tertiary care patients, newly-detected MRSA carriage confers large risks of infection and substantial attributable mortality in the year following acquisition. Most infections occur post-discharge, and 18% of infections associated with readmission occurred in hospitals other than the one where MRSA was newly-detected. Despite gains in reducing MRSA infections during hospitalization, the risk of MRSA infection among critically and chronically ill carriers persists after discharge and warrants targeted prevention strategies.
authors.affiliation: Division of Infectious Diseases and Health Policy Research Institute, School of Medicine, University of California Irvine, Irvine, California, United States of America. sshuang@uci.edu
authors.forename: Susan S
authors.initials: SS
authors.lastname: Huang
authors.forename: Virginia L
authors.initials: VL
authors.lastname: Hinrichsen
authors.forename: Rupak
authors.initials: R
authors.lastname: Datta
authors.forename: Laura
authors.initials: L
authors.lastname: Spurchise
authors.forename: Irina
authors.initials: I
authors.lastname: Miroshnik
authors.forename: Kimberly
authors.initials: K
authors.lastname: Nelson
authors.forename: Richard
authors.initials: R
authors.lastname: Platt
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D017714:Community-Acquired Infections / Q000175:diagnosis / Q000628:therapy; D005260:Female; D006760:Hospitalization / Q000706:statistics & numerical data*; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000472:pathogenicity*; D008875:Middle Aged; D010359:Patient Readmission / Q000706:statistics & numerical data; D012189:Retrospective Studies; D012306:Risk; D013203:Staphylococcal Infections / Q000175:diagnosis* / Q000628:therapy; D055815:Young Adult