title: Emergence of community-acquired methicillin-resistant Staphylococcus aureus USA 300 clone as the predominant cause of skin and soft-tissue infections.
abstract: BACKGROUND
  Studies have shown that community-acquired methicillin-resistant Staphylococcus aureus (MRSA) causes S. aureus skin and soft-tissue infection in selected populations.
  
  
  OBJECTIVE
  To determine the proportion of infections caused by community-acquired MRSA, the clinical characteristics associated with community-acquired MRSA, and the molecular epidemiology of community-acquired MRSA among persons with community-onset S. aureus skin and soft-tissue infection.
  
  
  METHODS
  Active, prospective laboratory surveillance to identify S. aureus recovered from skin and soft-tissue sources.
  
  
  METHODS
  1000-bed urban hospital and its affiliated outpatient clinics in Atlanta, Georgia.
  
  
  METHODS
  384 persons with microbiologically confirmed community-onset S. aureus skin and soft-tissue infection.
  
  
  METHODS
  Proportion of infections caused by and clinical factors associated with community-acquired MRSA among persons with community-onset S. aureus skin and soft-tissue infection. Pulsed-field gel electrophoresis and antimicrobial susceptibility patterns were used to epidemiologically classify community-onset S. aureus infections. Community-acquired MRSA was defined by MRSA isolates that either demonstrated a USA 300 or USA 400 pulsed-field type or had a susceptibility pattern showing resistance only to beta-lactams and erythromycin (for isolates not available for pulsed-field gel electrophoresis).
  
  
  RESULTS
  Community-onset skin and soft-tissue infection due to S. aureus was identified in 389 episodes, with MRSA accounting for 72% (279 of 389 episodes). Among all S. aureus isolates, 63% (244 of 389 isolates) were community-acquired MRSA. Among MRSA isolates, 87% (244 of 279 isolates) were community-acquired MRSA. When analysis was restricted only to MRSA isolates that were available for pulsed-field gel electrophoresis, 91% (159 of 175 isolates) had a pulsed-field type consistent with community-acquired MRSA; of these, 99% (157 of 159 isolates) were the MRSA USA 300 clone. Factors independently associated with community-acquired MRSA infection were black race (prevalence ratio, 1.53 [95% CI, 1.16 to 2.02]), female sex (prevalence ratio, 1.16 [CI, 1.02 to 1.32]), and hospitalization within the previous 12 months (prevalence ratio, 0.80 [CI, 0.66 to 0.97]). Inadequate initial antibiotic therapy was statistically significantly more common among those with community-acquired MRSA (65%) than among those with methicillin-susceptible S. aureus skin and soft-tissue infection (1%).
  
  
  CONCLUSIONS
  Some MRSA isolates were not available for molecular typing.
  
  
  CONCLUSIONS
  The community-acquired MRSA USA 300 clone was the predominant cause of community-onset S. aureus skin and soft-tissue infection. Empirical use of agents active against community-acquired MRSA is warranted for patients presenting with serious skin and soft-tissue infections.
authors.affiliation: Emory University School of Medicine and Grady Memorial Hospital, Atlanta, Georgia 30303, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: King
authors.forename: Bianca J
authors.initials: BJ
authors.lastname: Humphrey
authors.forename: Yun F
authors.initials: YF
authors.lastname: Wang
authors.forename: Ekaterina V
authors.initials: EV
authors.lastname: Kourbatova
authors.forename: Susan M
authors.initials: SM
authors.lastname: Ray
authors.forename: Henry M
authors.initials: HM
authors.lastname: Blumberg
mesh_terms: D044383:Black People; D017714:Community-Acquired Infections / Q000453:epidemiology / Q000382:microbiology; D016521:Electrophoresis, Gel, Pulsed-Field; D005260:Female; D005845:Georgia / Q000453:epidemiology; D006760:Hospitalization; D006801:Humans; D008297:Male; D016106:Methicillin Resistance; D012307:Risk Factors; D012737:Sex Factors; D018461:Soft Tissue Infections / Q000453:epidemiology / Q000382:microbiology*; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology*; D013207:Staphylococcal Skin Infections / Q000453:epidemiology / Q000382:microbiology*; D013211:Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000235:genetics*; D001741:Black or African American