title: Modeling the invasion of community-acquired methicillin-resistant Staphylococcus aureus into hospitals.
abstract: BACKGROUND
  Methicillin-resistant Staphylococcus aureus (MRSA) has traditionally been associated with infections in hospitals. Recently, a new strain of MRSA has emerged and rapidly spread in the community, causing serious infections among young, healthy individuals. Preliminary reports imply that a particular clone (USA300) of a community-acquired MRSA (CA-MRSA) strain is infiltrating hospitals and replacing the traditional hospital-acquired MRSA strains. If true, this event would have serious consequences, because CA-MRSA infections in hospitals would occur among a more debilitated, older patient population.
  
  
  METHODS
  A deterministic mathematical model was developed to characterize the factors contributing to the replacement of hospital-acquired MRSA with CA-MRSA and to quantify the effectiveness of interventions aimed at limiting the spread of CA-MRSA in health care settings.
  
  
  RESULTS
  The model strongly suggests that CA-MRSA will become the dominant MRSA strain in hospitals and health care facilities. This reversal of dominant strain will occur as a result of the documented expanding community reservoir and increasing influx into the hospital of individuals who harbor CA-MRSA. Competitive exclusion of hospital-acquired MRSA by CA-MRSA will occur, with increased severity of CA-MRSA infections resulting in longer hospitalizations and a larger in-hospital reservoir of CA-MRSA.
  
  
  CONCLUSIONS
  Improving compliance with hand hygiene and screening for and decolonization of CA-MRSA carriers are effective strategies. However, hand hygiene has the greatest return of benefits and, if compliance is optimized, other strategies may have minimal added benefit.
authors.affiliation: Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts 02215, USA. edagata@bidmc.harvard.edu
authors.forename: Erica M C
authors.initials: EM
authors.lastname: D'Agata
authors.forename: Glenn F
authors.initials: GF
authors.lastname: Webb
authors.forename: Mary Ann
authors.initials: MA
authors.lastname: Horn
authors.forename: Robert C
authors.initials: RC
authors.lastname: Moellering
authors.forename: Shigui
authors.initials: S
authors.lastname: Ruan
mesh_terms: D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission*; D003428:Cross Infection / Q000453:epidemiology* / Q000382:microbiology*; D006235:Hand Disinfection; D006801:Humans; D017053:Infection Control / Q000379:methods; D055624:Methicillin-Resistant Staphylococcus aureus / Q000302:isolation & purification*; D008962:Models, Theoretical; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology / Q000635:transmission*