Community-associated meticillin-resistant Staphylococcus aureus : the case for a genotypic definition

• Published in: The Journal of hospital infection 2012-07, Vol.81 (3), p.143-148
• Main Authors: Otter, J.A, French, G.L
• Format: Article
• Language: English
• Subjects: Bacterial diseases; Bacterial Typing Techniques; Biological and medical sciences; Community-Acquired Infections - epidemiology; Community-Acquired Infections - microbiology; Genotype; Human bacterial diseases; Humans; Infectious Disease; Infectious diseases; Medical sciences; Methicillin-Resistant Staphylococcus aureus - classification; Methicillin-Resistant Staphylococcus aureus - genetics; Molecular Epidemiology; Staphylococcal Infections - epidemiology; Staphylococcal Infections - microbiology; Staphylococcal infections, streptococcal infections, pneumococcal infections
• ISSN: 0195-6701; 1532-2939
• DOI: 10.1016/j.jhin.2012.04.009

Summary 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. Aim To review attempts to define CA-MRSA and propose a new definition. Methods Non-systematic review. Findings 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. Conclusion 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.