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MRSA in the ED: Plus Ça Change . . .

In a study of more than 400 patients presenting with skin and soft-tissue infections, 59% of all isolates were MRSA.

Healthcare-associated methicillin-resistant Staphylococcus aureus (MRSA) infections are a long-standing problem to which emergency medicine practice has adapted. Community-acquired MRSA, virtually unknown in 2000, is now prevalent (JWEM May 11 2005), but our ability to adapt has been limited by a lack of good information. To define the extent of the problem and to help clarify the role of antibiotics, researchers enrolled 422 patients with abscesses (81%), infected wounds (11%), and cellulitis with purulent drainage (8%) during August 2004. They performed sophisticated bacteriologic analysis on culture specimens, determined patient characteristics, and observed antimicrobial treatment and patient outcomes.

Fifty-nine percent of all isolates were MRSA, virtually all being the USA 300 type. Patient characteristics were not useful in determining which patients were likely to have MRSA. Of the isolates, 100% were sensitive to trimethoprim-sulfamethoxazole (TMP-SMX) and to rifampin, 95% to clindamycin, 92% to tetracycline, 60% to fluoroquinolones, and 6% to erythromycin. Nineteen percent of cases were treated with incision and drainage alone, 10% with antibiotics alone, 66% with both, and 5% with neither. In 100 of 175 cases of MRSA treated with antibiotics, the antibiotic choice was not concordant with the results of susceptibility testing. There was no significant difference in outcome between patients infected with MRSA and those infected with other bacteria, or between patients whose MRSA was resistant to the prescribed antibiotic and those in whom it was susceptible.

Comment: The 59% MRSA rate is striking, but the authors note two important points related to emergency practice: First, the treatment of an abscess is drainage. Second, this study did not include patients with nonpurulent cellulitis, which is usually caused by streptococci and not usually susceptible to TMP-SMX. Surprisingly, the authors strongly recommend that cultures be taken, despite a lack of supporting evidence and the fact that concordance of antibiotic therapy with susceptibility testing did not affect the outcome. Their other recommendation makes more sense: Antimicrobials should be used when clearly indicated (i.e., infected wounds or purulent cellulitis, as opposed to abscesses) and, when the diagnosis is indeterminate between ordinary cellulitis and a staph infection, the patient should be treated with both TMP-SMX and a ß-lactam agent.

— J. Stephen Bohan, MD, MS, FACP, FACEP

Published in Journal Watch Emergency Medicine September 8, 2006

Citation(s):

Moran GJ et al. Methicillin-resistant S. aureus infections among patients in the emergency department. N Engl J Med 2006 Aug 17; 355:666-74.

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• Medline abstract (Free)

Grayson ML. The treatment triangle for staphylococcal infections. N Engl J Med 2006 Aug 17; 355:724-7.

• Original article (Subscription may be required)
• Medline abstract (Free)