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Community-Acquired MRSA Enters U.S. Hospitals

New studies suggest an astonishingly high prevalence of this organism and hint at an unusual virulence.

Despite many recent descriptions of community-acquired methicillin-resistant Staphylococcus aureus (MRSA) outbreaks (Journal Watch Feb 18 2005), we know little about the prevalence of these infections. Results from three new studies add to our knowledge base.

In 2003 and 2004, researchers in an urban California emergency department screened for MRSA infection or nasal colonization in 137 adults who presented with localized skin or soft-tissue infections (primarily cellulitis, furunculosis, or wound infections). Of the 79 subjects with S. aureus isolated from their infected site, 61 (77%) had MRSA. All organisms were sensitive to trimethoprim-sulfamethoxazole; 94% were sensitive to clindamycin, 85% to tetracycline, and 57% to levofloxacin.

CDC researchers analyzed data on all MRSA infections reported by sentinel hospitals and laboratories in three U.S. locations in 2001 and 2002. Between 8% and 20% of infections were community-acquired, and 77% involved skin or soft tissue. Of the community-acquired isolates, 97% were sensitive to trimethoprim-sulfamethoxazole, 87% to clindamycin, 88% to tetracycline, and 65% to ciprofloxacin.

In a third report, researchers described 14 patients admitted to a Los Angeles hospital in 2003 or 2004 with necrotizing fasciitis caused by community acquired-MRSA. Ten patients had serious coexisting conditions, including diabetes, HIV infection, and cancer. Although all required extensive surgical débridement, none died. The five MRSA strains available for testing had identical genotypes that included the Panton-Valentine leukocidin gene that is associated with tissue destruction.

Comment: Given that mild community-acquired MRSA infections probably often go unidentified, these studies of severe infections suggest an astonishingly high prevalence of this organism and also hint at an unusual virulence. (S. aureus only rarely has been associated with necrotizing fasciitis in the past.) Authors and editorialists agree that these data spell the end for many routine protocols for dealing with staph infections, especially the selection of empirical antistaphylococcal treatment: First-generation cephalosporins are no longer indicated in areas with high prevalence of community-acquired MRSA and probably should not be used for unusually aggressive disease either. The first routine to change, of course, must be the all-too-common one of treating infections without performing cultures: Cultures now are more necessary than ever to guide the treatment of individual patients and to assess the community prevalence of MRSA.

— Abigail Zuger, MD

Published in Journal Watch General Medicine April 15, 2005

Citation(s):

Frazee BW et al. High prevalence of methicillin-resistant Staphylococcus aureus in emergency department skin and soft tissue infections. Ann Emerg Med 2005 Mar; 45:311-20.

• Medline abstract (Free)

Moran GJ and Talan DA. Community-associated methicillin-resistant Staphylococcus aureus: Is it in your community and should it change practice? Ann Emerg Med 2005 Mar; 45:321-2.

• Medline abstract (Free)

Fridkin SK et al. Methicillin-resistant Staphylococcus aureus disease in three communities. N Engl J Med 2005 Apr 7; 352:1436-44.

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

Miller LG et al. Necrotizing fasciitis caused by community-associated methicillin-resistant Staphylococcus aureus in Los Angeles. N Engl J Med 2005 Apr 7; 352:1445-53.

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

Chambers HF. Community-associated MRSA -- Resistance and virulence converge. N Engl J Med 2005 Apr 7; 352:1485-7.

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