title: Epidemiology of Staphylococcus aureus blood and skin and soft tissue infections in the US military health system, 2005-2010.
abstract: BACKGROUND
  Rates of hospital-onset methicillin-resistant Staphylococcus aureus (MRSA) infections are reported as decreasing, but recent rates of community-onset S. aureus infections are less known.
  
  
  OBJECTIVE
  To characterize the overall and annual incidence rates of community-onset and hospital-onset S. aureus bacteremia and skin and soft tissue infections (SSTIs) in a national health care system and to evaluate trends in the incidence rates of S. aureus bacteremia and SSTIs and the proportion due to MRSA.
  
  
  METHODS
  Observational study of all Department of Defense TRICARE beneficiaries from January 2005 through December 2010. Medical record databases were used to identify and classify all annual first-positive S. aureus blood and wound or abscess cultures as methicillin-susceptible S. aureus or MRSA, and as community-onset or hospital-onset infections (isolates collected >3 days after hospital admission).
  
  
  METHODS
  Unadjusted incidence rates per 100,000 person-years of observation, the proportion of infections that was due to MRSA, and annual trends for 2005 through 2010 (examined using the Spearman rank correlation test or the Mantel-Haenszel χ2 test for linear trend).
  
  
  RESULTS
  During 56 million person-years (nonactive duty: 47 million person-years; active duty: 9 million person-years), there were 2643 blood and 80,281 wound or abscess annual first-positive S. aureus cultures. Annual incidence rates varied from 3.6 to 6.0 per 100,000 person-years for S. aureus bacteremia and 122.7 to 168.9 per 100,000 person-years for S. aureus SSTIs. The annual incidence rates for community-onset MRSA bacteremia decreased from 1.7 per 100,000 person-years (95% CI, 1.5-2.0 per 100,000 person-years) in 2005 to 1.2 per 100,000 person-years (95% CI, 0.9-1.4 per 100,000 person-years) in 2010 (P = .005 for trend). The annual incidence rates for hospital-onset MRSA bacteremia also decreased from 0.7 per 100,000 person-years (95% CI, 0.6-0.9 per 100,000 person-years) in 2005 to 0.4 per 100,000 person-years (95% CI, 0.3-0.5 per 100,000 person-years) in 2010 (P = .005 for trend). Concurrently, the proportion of community-onset SSTI due to MRSA peaked at 62% in 2006 before decreasing annually to 52% in 2010 (P < .001 for trend).
  
  
  CONCLUSIONS
  In the Department of Defense population consisting of men and women of all ages from across the United States, the rates of both community-onset and hospital-onset MRSA bacteremia decreased in parallel, while the proportion of community-onset SSTIs due to MRSA has more recently declined.
authors: Infectious Disease Service, San Antonio Military Medical Center, Fort Sam Houston, Texas 78234, USA.
authors: Michael L
authors: ML
authors: Landrum
authors: Charlotte
authors: C
authors: Neumann
authors: Courtney
authors: C
authors: Cook
authors: Uzo
authors: U
authors: Chukwuma
authors: Michael W
authors: MW
authors: Ellis
authors: Duane R
authors: DR
authors: Hospenthal
authors: Clinton K
authors: CK
authors: Murray
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D016470:Bacteremia / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D017714:Community-Acquired Infections / Q000453:epidemiology; D003428:Cross Infection / Q000453:epidemiology; D016208:Databases, Factual; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus; D008875:Middle Aged; D008889:Military Personnel / Q000706:statistics & numerical data*; D012189:Retrospective Studies; D018461:Soft Tissue Infections / Q000453:epidemiology*; D013203:Staphylococcal Infections / Q000453:epidemiology*; D013207:Staphylococcal Skin Infections / Q000453:epidemiology*; D014481:United States / Q000453:epidemiology; D055815:Young Adult