Methicillin-resistant Staphylococcus aureus in community-acquired and health care-associated pneumonia: incidence, diagnosis, and treatment options.

Pneumonia is one of the leading causes of death in the United States. As health care has expanded into community settings, including outpatient clinics, long-term care facilities, and dialysis centers, a new category of pneumonia-health care-associated pneumonia (HCAP)-has been defined. Bacterial resistance to antibiotics is rising among community-acquired infections, and the emergence of community-associated methicillin-resistant Staphylococcus aureus (MRSA) infections, particularly the severe form of necrotizing pneumonia mediated by USA 300 in young and healthy individuals, warrants attention. Although Streptococcus pneumoniae remains the most prevalent causative pathogen in community-acquired pneumonia (CAP), S aureus infections are increasingly being reported in community settings, especially in patients with HCAP. Recent surveillance of community-dwelling adults with pneumonia admitted to United States hospitals has demonstrated a steady increase in S aureus isolates. Thus, MRSA should be considered in severe pneumonia associated with influenza-like symptoms, particularly when accompanied by hemoptysis or leukopenia. However, MRSA pneumonia also can develop in the absence of preceding influenza-like illness. Effective empiric therapy for pneumonia, whether CAP or HCAP, mandates selection of an agent with coverage against all likely pathogens. Failure to provide adequate initial antimicrobial coverage has been associated with an increased risk of death. The spread of resistant pathogens in the community challenges currently available antimicrobial agents for effective treatment of MRSA-mediated pneumonia. Approval of newer antimicrobials with MRSA activity may provide additional options for the management of pneumonia. This article provides a review of the role of MRSA as a causative pathogen in CAP and HCAP.