Community-acquired MRSA: A Notable Adversary

Authors: John S. Francis, MD, PHD, Karen Carroll, MD


In this issue, Clancy et al1 describe their findings from a retrospective cohort study conducted in 2003 on 193 patients evaluating the epidemiology, outcomes, and molecular characterization of community-acquired Staphylococcus aureus (CA-SA) infections from an integrated health care system serving the center of metropolitan Denver. Their data confirm the observation of others in the United States 2–4 and worldwide5 that community-acquired methicillin-resistant S aureus (CA-MRSA) strains have markedly increased, rising from 6 to 45% (P < 0.001) in Denver over a period of 2 years, and that the typical risk factors associated with MRSA may not be present in such individuals. Clancy et al found that their CA-MRSA strains were mostly of a similar pulsed-field type (speculated by the authors to be USA 300) and more likely to have high rates of quinolone resistance (51%) compared with methicillin-susceptible strains (3%). In addition, 10 of 20 CA-MRSA isolates tested positive for the Panton-Valentine leukocidin (PVL) gene, which code for a known CA-SA virulence factor.1

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