title: Community-associated meticillin-resistant Staphylococcus aureus: the case for a genotypic definition.
abstract: BACKGROUND
  New distinct strains of community-associated meticillin-resistant Staphylococcus aureus (CA-MRSA) have emerged as a cause of infection in previously healthy individuals in community settings. It is important to identify CA-MRSA for clinical management, epidemiological analysis, infection prevention and control, and regulatory reporting, but definitions and nomenclature of these strains are confused.
  
  
  OBJECTIVE
  To review attempts to define CA-MRSA and propose a new definition.
  
  
  METHODS
  Non-systematic review.
  
  
  RESULTS
  Epidemiological definitions were useful for differentiating CA-MRSA and healthcare-associated (HA)-MRSA strain types in the past. However, although HA-MRSA strain types are rarely transmitted in the community, CA-MRSA strains have started to be transmitted in healthcare facilities, so epidemiological definitions are breaking down. CA-MRSA are community strains of S. aureus that have acquired the meticillin resistance gene, mecA. They are distinct from HA-MRSA and should be defined genetically. This may be done by combining genotypic typing by multi-locus sequence or spa with analysis of the staphylococcal cassette chromosome mec. Carriage of Panton-Valentine leukocidin or antimicrobial susceptibility profiles can be useful indicators of CA-MRSA but should not be used for their definition.
  
  
  CONCLUSIONS
  For full assessment of their epidemiology, MRSA infections should be characterized as: (1) caused by HA- or CA-MRSA strain types; (2) acquired in community or healthcare settings; and (3) onset in the community or healthcare facility.
authors.affiliation: Centre for Clinical Infection and Diagnostic Research (CIDR), Department of Infections Diseases, King's College London School of Medicine, London, UK. jonathan.otter@kcl.ac.uk
authors.forename: J A
authors.initials: JA
authors.lastname: Otter
authors.forename: G L
authors.initials: GL
authors.lastname: French
mesh_terms: D015373:Bacterial Typing Techniques; D017714:Community-Acquired Infections / Q000453:epidemiology* / Q000382:microbiology; D005838:Genotype; D006801:Humans; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics*; D017720:Molecular Epidemiology; D013203:Staphylococcal Infections / Q000453:epidemiology* / Q000382:microbiology