Etiology and treatment of community-associated methicillin-resistant Staphylococcus aureus

Risk factors and treatment recommendations for community-associated methicillin-resistant Staphylococcus aureus are reviewed.

A new strain of methicillin-resistant Staphylococcus aureus (MRSA) has prompted researchers to examine the factors associated with infections acquired in outpatient settings as opposed to those that develop nosocomially. Infections of the skin, lungs, urinary tract, and bloodstream diagnosed within 24-72 hours of hospitalization and with no risk factors present were categorized as community-associated MRSA (CA-MRSA) and differentiated from health-care-associated methicillin-resistant S. aureus (HA-MRSA) on a molecular basis. Pulsed-field electrophoresis has been instrumental in genotyping the S. aureus organism to identify bacterial isolates. Molecular differences between community- and hospital-associated strains show that the organisms were genetically distinct and had not migrated to other settings. Some studies examining antibiotic resistance indicated a steady increase in the rate of MRSA infections. In addition, results of a 15-year longitudinal study indicated significant increases in CA-MRSA-positive isolates between 1991 and 2004. Race, age, sex, hygiene, living environment, and socioeconomic status have been shown to play a key role in the incidence of CA-MRSA.

Health care providers should recognize how CA-MRSA and HA-MRSA are differentiated and what factors are associated with infections caused by the organisms. This will enable health care providers to quickly identify and initiate appropriate treatment for these infections.