title: Changing epidemiology of community-onset methicillin-resistant Staphylococcus aureus bacteremia.
abstract: OBJECTIVE
  To review cases of community-onset Staphylococcus aureus bacteremia and to evaluate whether the risk factors and epidemiology of methicillin-resistant S. aureus (MRSA) bacteremia have changed from early reports.
  
  
  METHODS
  Retrospective case-comparison study of community-onset MRSA (n = 26) and methicillin-susceptible S. aureus (MSSA) (n = 26) bacteremias at our institution.
  
  
  METHODS
  A 600-bed urban academic medical center.
  
  
  METHODS
  Twenty-six patients with community-onset MRSA bacteremia were compared with 26 patients with community-onset MSSA bacteremia. Molecular analysis was performed on S. aureus isolates from the 26 MRSA cases as well as from 13 cases of community-onset S. aureus bacteremia from 1980 and 9 cases of nosocomial S. aureus bacteremia from 2001.
  
  
  RESULTS
  The two groups were similar except that patients with MRSA bacteremia were more likely to have presented from a long-term-care facility (26.9% vs 4%; P = .05) and to have had multiple admissions within the preceding year (46% vs 15%; P = .03). Clamped homogeneous electric fields analysis of MRSA isolates from 1982 revealed predominantly that one clone was the epidemic strain, whereas there were 14 unique strains among current community-onset isolates. Among current nosocomial isolates, 3 patterns were identified, all of which were present in the community-onset cases.
  
  
  CONCLUSIONS
  Previously described risk factors for MRSA acquisition may not be helpful in predicting disease due to the polyclonal spread of MRSA in the community. Unlike early outbreaks of MRSA in patients presenting from the community, current acquisition appears to be polyclonal and is usually related to contact with the healthcare system.
authors.affiliation: St. John Hospital and Medical Center, Wayne State University, Detroit, Michigan 48236, USA.
authors.forename: Leonard B
authors.initials: LB
authors.lastname: Johnson
authors.forename: Arti
authors.initials: A
authors.lastname: Bhan
authors.forename: Joan
authors.initials: J
authors.lastname: Pawlak
authors.forename: Odette
authors.initials: O
authors.lastname: Manzor
authors.forename: Louis D
authors.initials: LD
authors.lastname: Saravolatz
mesh_terms: D000046:Academic Medical Centers; D000368:Aged; D016470:Bacteremia / Q000453:epidemiology* / Q000209:etiology / Q000382:microbiology; D002408:Catheters, Indwelling / Q000009:adverse effects / Q000382:microbiology; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology; D004696:Endocarditis / Q000150:complications / Q000382:microbiology; D005260:Female; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D008824:Michigan; D008875:Middle Aged; D012189:Retrospective Studies; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology; D013211:Staphylococcus aureus / Q000302:isolation & purification*