Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is responsible for an increasing number of pneumonia cases among otherwise healthy, younger patients, according to a recent literature review.

“Necrotizing pneumonia due to CA-MRSA is now recognized as an emerging clinical entity with distinctive clinical features and substantial morbidity and mortality,” report Alicia I. Hidron, MD, and colleagues at Emory University School of Medicine in Atlanta (Lancet Infect Dis. 2009;9:384-392). “This entity should be suspected in patients presenting from the community with sepsis, hemoptysis, multilobar infiltrates, and leukopenia.”

Once limited to older and other high-risk patients in particular hospitals, MRSA infections “now occur widely both in the community as well as health-care facilities,” the team reports. But CA-MRSA and hospital-acquired MRSA are not quite the same agents, and CA-MRSA is more responsive to antibiotic treatment.

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Patients typically present with high fever and low BP, then rapidly progress to septic shock and the need for mechanical ventilation. Mortality rates higher than 50% have been reported in the United States and Europe, the researchers state.

CA-MRSA often manifests as a skin or soft-tissue infection, but pneumonia accounts for about 2% of cases in the United States. These patients usually start with flulike viral symptoms followed by acute onset of shortness of breath, sepsis, and hemoptysis.

“In such patients, [providing] standard treatment of community-acquired pneumonia will be inappropriate,” the researchers assert, recommending that vancomycin or linezolid therapy start immediately, pending culture results.

The condition “may have special relevance given the emergence of H1N1 influenza,” the authors add.