Healthy people are increasingly being infected with methicillin-resistant Staphylococcus aureus (MRSA). A study published in the New England Journal of Medicine reports that community-acquired MRSA caused 59% of skin and soft-tissue infections seen in the EDs of 11 U.S. cities in August 2004. Genetic and phenotypic analysis showed that most of the community outbreaks were caused by the USA300 strain and that almost all contained Panton-Valentine leukocidin (pvl) genes, the toxin of which is associated with spontaneous skin and bone infections and necrotizing pneumonia.

These findings are important because while community-acquired MRSA has retained sensitivity to some antibiotics-including trimethoprim-sulfamethoxazole, tetracycline-doxycycline, and clindamycin-more than half of the patients in this study received antibiotics to which the isolate was resistant. Wherever MRSA is the most common cause of purulent skin and soft- tissue infections, standard precautions should be observed; also, abscesses should be drained, wounds should be cultured, and empiric antibiotic treatment should begin with one of the above-mentioned agents, pending culture and sensitivity results.

A study by Pannaraj and colleagues found MRSA to be the cause of a doubling of cases between 2000 and 2005 of primary pyomyositis and myositis associated with community- acquired MRSA atTexas Children's Hospital in Houston. MRSA was found in 33% of cases of primary pyomyositis or myositis; all strains were type USA300, and 81% had pvl genes. Muscle drainage was required to treat 81% of infections that were positive for MRSA, pvl genes, or both, and 24% required repeated drainage.

Fran Mennick, BSN, RN